System option modes for VSP 5000 series

Mode 15 = ON (default):

• Upper limit for retry of drive is reduced from 2 sec. to 0.5 sec.
• If a drive failure occurs in read processing, a correction read processing is executed immediately.
• I/O watching time is changed from 6.5 sec. to 4.5 sec. (I/O watching time including DMA transfer is 10 sec.)
• Read or write processing is not retried for time-out failure.

Mode 15 = OFF:

• Upper limit for retry of drive is 2 sec.
• If a drive failure occurs in read processing, a retry processing corresponding to the type of failure is executed.
• I/O watching time is 6.5 sec. (I/O watching time including DMA transfer is 10 sec.)
• Read or write processing is retried for time-out failure.

Notes:

1. This SOM applies at a site where a drive response delay may affect business operations.
2. When Dynamic Sparing or Auto Correction Mode is used, because host I/Os conflict with copy processing, the I/O watching time is 30 seconds even when this SOM is set to ON.
3. Even though SOM 15 is set to ON, the function does not apply to SATA or NL-SAS drives.
4. When SOM 771 or SOM 797 is set to ON, the setting of SOM 771/797 is prioritized for the read I/O watching time.
5. For additional details about this SOM (interaction with other SOMs, operational details), contact customer support (see SOM015 sheet).

Conditions:

• TCz P-VOL
• Mainframe volume
• Pair status: Duplex/Pending

Mode 64 = OFF (default):

• When receiving the Freeze command, pairs that fulfill the conditions below are suspended and the SCP is set. In the case of CU emulation type 2105/2017, the path between MCU and RCU is deleted, while the path is not deleted but unusable with Query displayed only in the case of CU emulation type 3990.
• When receiving the RUN command, the SCP status of the pairs that fulfill the conditions below is released.
• When a Failure Suspend occurs while the Freeze Option Enable is set, except the pair in which the Failure Suspend occurs, other pairs that fulfill the conditions below go into SCP state.

Conditions:

• TCz P-VOL
• Mainframe volume
• Pair status: Duplex/Pending
• A pair whose RCU# is identical to the RCU for which the Freeze command is specified.

Notes:

1. General use: SOM 64 = OFF (default).
2. When all the following conditions are met, set SOM 64 to ON:
   • Customer requests to stop the update I/O operation to the RCU of a TCz pair for the whole storage system.
   • Disaster Recovery function such as GDPS, HyperSwap, or Fail Over/ Fail Back, which requires compatibility with IBM^® storage, is not used as SOM 64 operates without having compatibility with IBM^® storage.
   • Only Peer-to-Peer-Remote-Copy operation. (Do not use it in combination with Business Continuity Manager.)
3. Even though the Failover command is not an applicable criterion, when executing the Failover command while SOM 114 is ON, since ports are not automatically switched, the Failover command fails.
4. With increase of Sync pairs in storage system, the time period to report the completion of Freeze command and RUN command gets longer (estimate of time to report completion: 1 second per 1000 pairs), and MIH may occur.

Notes:

1. If an incorrect port is selected while this SOM is set to ON, and if ESTPATH is executed when no logic path exists, the port is switched to RCP.
2. If TPC-R (IBM^® software for disaster recovery), set this SOM to OFF.
3. For Fibre Channel interface, do not use the CESTPATH and CDELPATH commands at the same time as the SCSI path definition function. Fibre Channel interface ports need to be configured as initiator ports or RCU target ports before the CESTPATH and CDELPATH commands are issued.

Notes:

1. This SOM should always be set to ON. This SOM can be set to OFF only when the customer does not allow to set this SOM to ON for a storage system already in production.
2. Settings of SOM 363, SOM 365, and SOM 809 are related each other. The order of priority for the setting to be enabled is SOM 809, SOM 363, SOM 365, and then SOM 142. For details, contact customer support (see the mode document of each SOM).
3. This SOM is effective for the entire storage system.

Notes:

1. Data is not secured at the failure on both sides of CM/SM. Recovery from all volume backups is required.
2. Determine whether to set the mode to ON or OFF on the following basis:

   OFF: The mode is set to OFF to secure the data even when a CM/SM dual failure occurs. As the write through works for data assurance at CM/SM one-side blockage, make sure to design a system where performance degradation such as I/O response is acceptable in a configuration where data from host is duplicated on primary and secondary storages.

   ON: The mode is set to ON to prioritize maintaining the performance over data assurance as a single storage system when a CM/SM dual failure occurs. When the mode is set to ON, the data may be lost at the CM/SM dual failure. If high data reliability is required for the storage system like RAID, data duplication should be realized by the entire system like a configuration where data from host is duplicated on primary and secondary storages.

3. Using this SOM poses a risk of losing the data at a CM/SM dual failure. If high data reliability is required for the storage system like RAID, data duplication should be realized by the entire system like the configuration in which data from host is duplicated on primary and secondary storages.
4. When this SOM is used, the time required for blocking cache memory/shared memory at maintenance is longer than that when this SOM is set to OFF so that the maintenance operation may end abnormally if the amount of write pending is large. Therefore, perform the maintenance operation when the amount of write pending is as less as possible. If the maintenance operation ends abnormally, replace the blocked part to recover.
5. When setting the function to each LDEV is desired, contact customer support. (See "WR Through" function on the System Option window. See 2.13 System option in the SVP section of Maintenance Manual. Also, follow the above (1) even when the "WR Through" is used.)

Notes:

1. This SOM is applied along with SOM 20 when data writing to a VTOC area in the S-VOL of a suspended TCz pair is required.
2. If a write I/O is issued wrongly to an S-VOL VTOC area of a suspended TCz pair, the consistency between the P-VOL and the S-VOL is lost, but the inconsistency is solved by a resume operation.

Notes:

1. Set SOM 305 to ON before performing LDEV Format for a mainframe volume if you want to perform OS IPL (volume online) without fully initializing the volume after the LDEV Format. However, full initialization is required in actual operation.
2. Processing time of LDEV format increases by as much as full initialization takes.
3. The following functions and conditions are not supported:
   • Quick format
   • 3390-A (Dynamic Provisioning attribute)
   • Volume Shredder
4. Full initialization is required in actual operation.

Notes:

1. This SOM applies to a site where strict host response performance is required.
2. If a hardware failure occurs when this SOM is set to ON, the time until MPB blockage that is determined is shorter than usual.

Notes:

1. When this SOM is set to ON, even if there is an overloaded CLPR (CLPR with large Write Pending capacity), the amount of destage processing would not increase easily. Therefore TOV(MIH) may occur in the overloaded CLPR. Set this SOM to ON only when the overloaded state of a specific CLPR would not affect other CLPRs.

   When the UR function is used, if user volumes and journal volumes are defined in different CLPRs, when the CLPR to which the journal volumes are assigned overflows, the user volumes become inaccessible. Therefore it is recommended to set this SOM to OFF.

2. Because the destage processing will have a lower priority in the overloaded CLPR, the overloaded state of the overloaded CLPR is not removed, and TOV(MIH) might occur.

Notes:

1. Apply the mode for users who require that de-staging S-VOL data to an external volume mapped to the S-VOL has been completed when the pair status changes to PSUS.
2. The function works for the pairs created while the mode is set to ON and does not work for the pairs created while the mode is set to OFF.
3. Because de-staging takes place after the copy is complete, the time required to change the status from PSUS(SP) or COPY(SP) to PSUS increases.
4. When both of SOM 459 and SOM 1263 are used, the throughput improvement by setting SOM 1263 to ON cannot be expected.
5. At a split operation, the time required to change the status to PSUS when the mode is ON gets longer than that when the mode is set tot OFF.

Notes:

1. It takes longer to finish the copy processing because it stops for prioritizing the host I/O performance.
2. This SOM supports background copy only. The processing to copy the pre-update data to the S-VOL, which occurs when overwriting data to uncopied slots of P-VOL in Split processing or reading or writing data to uncopied slots of S-VOL, is not supported.
3. Check the write pending rate of each CLPR per MP unit. Even though there is some free cache capacity in the entire system, if the write pending rate of an MP unit to which pairs* belong exceeds the threshold, the copy operation is stopped.

   *Applies to pairs of SI, SIz, FCv2, FCSE, and Volume Migration.

Notes:

1. Set this SOM for both primary and secondary storage systems.
2. When this SOM is set to ON:
   • Execute all pair operations from CCI/BCM.
   • Use a dedicated script.
   • Initial copy operation is prioritized over update I/O. Therefore, the processing speed of the update I/O slows down.
3. If this SOM is set to ON, the processing speed of update I/O slows down by about 15 μs per command, version downgrade is disabled, and Take Over is not available.
4. If this SOM is not set to ON for both sides, the behavior is as follows:
   • OFF in primary and secondary storage systems: Normal UR initial copy performance.
   • ON in the primary storage system/OFF in the secondary storage system: TC Sync pair creation fails.
   • OFF in the primary storage system/ON in the secondary storage system: The update data is copied to the S-VOL synchronously.
5. While this SOM is set to ON, make sure not to perform microcode downgrade to an unsupported version.
6. While this SOM is set to ON, make sure not to perform the Take Over function.
7. This SOM cannot be applied to a UR pair that is the second mirror in a URxUR multi-target configuration, URxUR cascade configuration, or 3DC multi-target or cascading configuration of three UR sites. If applied, TC pair creation is rejected with SSB=CBED output.
8. Before setting SOM 474 to ON, make sure that SOM 1091 is set to OFF. If SOM 1091 is set to ON, set it to OFF first, and then set SOM 474 to ON.

Notes:

1. Set this SOM to ON when you want to maintain compatibility with the Previous Spec for PPRC path QUERY display under the environment where IBM host function (such as PPRC and GDPS) is used.
2. If the display specification is different between MCU and RCU, it may cause malfunction of host.
3. When IBM^® TPC-R or CSM software for disaster recovery is used, set this SOM to ON.

Mode 506 = ON (default):

• Without update I/O: Delta Resync is enabled.
• With update I/O: Delta Resync is enabled.

Mode 506 = OFF:

• Without update I/O: Total data copy of Delta Resync is performed.
• With update I/O: Delta Resync is enabled.

Notes:

1. When Command Device is used online, if a script containing an operation via Command Device has been executed, the script may stop if this SOM is set to ON. As described in the BCM user’s guide, the script must be performed with Command Device offline.
2. This SOM is applied to operations from BCM that is operated on MVS.

Notes:

1. When CU emulation type is 2105/2107, this SOM is applied in the case where pair creation in TCz – SIz cascading configuration in the ICKDSF environment fails with the following message output:

   Message: ICK30111I DEVICE SPECIFIED IS THE SECONDARY OF A DUPLEX OR PPRC PAIR

2. This SOM is applied when building an environment using the Metro Mirror F.O./F.B. function with TPC-R or CSM.
3. The CASCADE option can be specified in the TSO environment also.
4. Although the CASCADE option can be specified for the ESTPAIR command, the PPRC-XD function is not supported.
5. Perform thorough pre-check for any influence on GDPS/PPRC.
6. The SOM must be enabled only when the CASCADE option is specified for the ESTPAIR command for the CU emulation type 2105/2107.

Notes:

1. This SOM is applied if SIMs (RC=DCE0 to DCE3) need to be reported to a Mainframe host.
2. The SIMs are not reported to the Open server.
3. SIMs for JNL full (RC=DCE0 and DCE1) on MCU are reported to the host connected with MCU.
4. SIMs for JNL full (RC=DCE2 and DCE3) on RCU are reported to the host connected with RCU.

Notes:

1. Apply this SOM if suspending pairs, preventing journals from being accumulated, and notifying the error to users are preferred rather than allowing journal accumulation and eventual failure suspension due to journal full when the communication between CCI and the storage system in the primary site is unavailable in a consistency group configuration.
2. When this SOM is set to ON, set the interval of issuing time stamps from CCI to 4 minutes or less (about 1 second is recommended). If greater than 4 minutes is set, the function may work 5 minutes after a temporary communication error, etc.
3. To stop a CCI instance for 5 minutes or longer for CCI configuration definition file rewriting or server maintenance, set this SOM to OFF.
4. If the DKCMAIN microcode is downgraded to an unsupported version while this SOM is set to ON, and then the microcode is to be upgraded to the supported version, set this SOM to OFF before the microcode upgrade.

Notes:

1. This SOM is applied if reporting Byte1,Bit5 (VPD flag) = ON when the PPRC ESTPAIR CRIT option is "NO" (Fence level = NEVER) and VPD (SOM36) is ON is required.
2. The behavior of CRIT (=fence level) itself does not change and is the same as PPRC ESTPAIR CRIT (NO).

Notes:

1. This SOM is applied to obtain the SIz pair information by the SenseSubSystem command when a TCz pair is in SSWS status or write access to the S-VOL is permitted in a configuration where the TCz pair is conbined with an SIz pair.
2. When SOM 640 is ON, VARY ONLINE cannot be run for a volume shared by a TCz S-VOL and anSIz P-VOL volume.

Notes:

1. This SOM can be set online.
2. The micro-programs on both MCU and RCU must support this SOM.
3. This SOM should be set when requested by the user.
4. Setting this SOM to ON is recommended when GAD is installed, as the performance degradation is more likely to occur due to active-active I/Os.
5. If the Write Pending status remains at 60% or more on the RCU for a long time, it takes extra time for the initial copy and resync copy to be completed due to slowed down copy operations.
6. If the Write Pending rate of CLPR to which the initial copy target S-VOL belongs is not over 60% but that of MP PCB to which the S-VOL belongs is over 60%, the initial copy operation is slowed down.
7. When this SOM is applied while an unsupported model (USP V/VM earlier than V02) is connected as MCU, if the Write Pending rate reaches 60%, pair suspend may occur.
8. As the mode is enabled per storage system, in an environment where TC and GAD are used, the mode is applied to both program products. When GAD is installed in a storage system that already uses TC, TC initial copy may take longer time.

Notes:

1. This SOM can be set online.
2. This SOM should be set per customer’s requests.
3. If the Write Pending status long keeps 60% or more on RCU, it takes extra time for the initial copy to be completed by making up for the prevented copy operation.
4. If the Write Pending status long keeps 60% or more on RCU, the pair status may become Suspend due to the JNL-Vol being full.

Notes:

1. When the external storage is TagmaStore USP/NSC and the Open LDEV Guard attribute (VMA) is defined on an external device, set this SOM to ON.
2. When this SOM is set to ON, it takes longer time to complete the LU discovery. The amount of time depends on external storages.
3. With this SOM OFF, if searching for external devices with VMA is set, the VMA information cannot be read.
4. When this SOM is set to ON while the following conditions are met, the external volume is blocked:
   • An external volume to which Nondisruptive migration (NDM) attribute is set exists.
   • The external volume is reserved by the host
5. As the VMA information is TagmaStore USP/NSC-specific, this SOM does not need to be ON when the external storage is other than TagmaStore USP/NSC.
6. Set this SOM to OFF when an external volume to which nondisruptive migration (NDM) attribute is set exists.

Notes:

1. Apply this SOM when the load of host I/O to an ECC that uses ShadowImage or Volume Migration is high and the host I/O processing is delayed.
2. If the PDEV is highly loaded, the priority of Read/Write processing made by ShadowImage, Volume Migration, or Resync may become lower. As a consequence the copy speed may be slower.

Notes:

1. When the RAID level or emulation type is changed for the existing parity group, this SOM should be applied only if the drive mounted position remains the same at the time of the parity group uninstallation or installation.
2. After the operation using this SOM is completed, this SOM must be set back to OFF; otherwise, the LED of the drive to be removed will not be illuminated at subsequent parity group uninstalling operations.

Notes:

1. Applying this SOM is prohibited when USP V/VM is used as external storage system and its external volume is DP-VOL.
2. Applying this SOM is recommended when the above condition (1) is not met and SUN storage is used as an external storage.
3. Applying this SOM is recommended when the above condition (1) is not met and EMC CX series or Fujitsu Fibre CAT CX series is used as an external storage.
4. Applying this SOM is recommended if the above condition (1) is not met and a maintenance operation such as firmware update causing controller reboot is executed on the external storage side while a storage system other than Hitachi product is used as an external storage system.
5. While USP V/VM is used as an external storage system and its volume is DP-VOL, if some Pool-VOLs constituting the DP-VOL are blocked, external path blockade and recovery occurs repeatedly.
6. When a virtual volume mapped by UVM is set to pool-VOL and used as DP-VOL in local storage system, this SOM can be applied without problem.

Notes:

1. This SOM is turned ON to prevent the write I/O operation from being unavailable due to pool full.
2. If the pool threshold exceeding SIM occurs frequently, other SIMs may not be reported.
3. Though turning on this SOM can increase the warning effect, if measures such as adding a pool fail to be done in time so that the pool becomes full, SOM 729 can be used to prevent file systems from being destroyed.
4. Turning on SOM 741 can provide the SIM report to both the users and the service personnel.
5. If SIM=62B000 remains uncompleted, the SIM is not reported to SVP.

Notes:

1. This SOM is set to ON to have SIM for users reported to the service personnel:
   • For the system where SNMP and E-mail notification are not set.
   • If Device Manager - Storage Navigator is not periodically activated.
2. When SOM 734 is turned OFF, SIM-RC625000 is not reported; accordingly the SIM is not reported to the service personnel even though this SOM is ON.

Notes:

1. This SOM is applied when the EMC SYMMETRIX is connected using UVM.
2. Enable the setting of EMC SCSI Flag SC3 for the port of the EMC SYMMETRIX storage connected with the storage system and disable the setting of Flag SPC2. If the setting of EMC SCSI Flag SC3 is not enabled or the setting of Flag SPC2 is enabled, the effect of this SOM may not be achieved.
3. If you want to enable this SOM immediately after setting, perform Check Paths on each path one by one for all the external ports connected to the EMC SYMMETRIX storage. But, without doing Check Paths, the display of Characteristic1 can automatically be changed by the Device Health Check to be performed once an hour. If SSB=AD02 occurs and a path is blocked, perform Check Paths on this path again.
4. If the Check Paths is performed while ShadowImage for Mainframe pair and FlashCopy^® Mirror pair are defined in the specified volume, the Check Paths operation is rejected with a message, "605 2518". If ShadowImage for Mainframe pair and FlashCopy^® Mirror pair are defined in the specified volume, do not perform Check Paths but wait until the display is automatically changed.

Notes:

1. This SOM is applied when no change in performance characteristic is desired.
2. When a pool is newly installed, the load may be concentrated on the installed pool volumes.
3. When 0 data discarding is executed, load may be unbalanced among pool volumes.
4. Pool VOL deletion while this SOM is set to ON fails. To delete pool VOLs, set this SOM to OFF.

Notes:

1. This SOM applies to the sites where outputting the In-band audit logs is not needed.
2. When this SOM is set to ON:
   • There is no access to SM for the In-band audit logs, which can avoid the corresponding performance degradation.
   • SM is not used for the In-band audit logs.
3. If outputting the In-band audit log is desired, set this SOM to OFF.

Notes:

1. This SOM is applied under the following conditions.
   • Universal Replicator for Mainframe.
   • EXCTG configuration.
   • Flush suspension with an EXCTG specified is executed.
   • BCM is installed on the host where the time stamping function is available.
   • (In the case of multiple-host configuration, SYSPLEX timer is available on the system)
2. If this SOM is set to ON while the BCM does not exist in the environment where the time stamping function is available (In the case of multiple-host configuration, SYSPLEX timer is available on the system), the pair status may not become Suspend after Flush suspension for an EXCTG.
3. Do not set this SOM to ON if the BCM does not exist in the environment where the time stamping function is available (In the case of multiple-host configuration, SYSPLEX timer is available on the system).

Notes:

1. Apply this SOM when the following three conditions are met:
   • SOM 114 is set to OFF (operation of automatically switching the port is disabled).
   • HMO 49 and HMO 50 are set to OFF.
   • TPC-R or CSM is used (it is not applied in normal operation).
2. When SOM 769 is set to ON, SOM 114, HMO 49, and HMO 50 must be set to OFF.
3. In either of the following cases, the path creation operation might fail after automatic port switching is executed.
   • SOM 114 is set to ON.
   • HMO 49 and HMO 50 are set to ON.

Notes:

1. Set this SOM to ON in the environment where TCz is used from BCM and the MCU host does not need the F/M=FB message output during an S-VOL pair suspend or pair delete operation from BCM.
2. When this SOM is set to ON, the F/M=FB message is not output to the host when the status of P-VOL changes to Suspend during a TCz S-VOL pair suspend or pair delete operation from BCM.
3. If the PPRC item of CU option is set to NO, the F/M=FB message is not output to the host regardless of setting of this SOM.
4. If the function switch#07 is set to "enable", the F/M=FB message is not output to the host regardless of setting of this SOM.

Notes:

1. This SOM is applied to the environment where Mainframe host MIH time is set to 15 seconds.
2. This SOM is applied to the environment where OPEN host time-out time is set to 15 seconds or less.
3. This SOM is applied to reduce RI/O MIH time to 5 seconds.
4. This function is available for all the TC, TCz, and GAD pairs on the storage system, unable to specify the pairs that are using this function or not.
5. To apply this SOM to TCz, MCU and RCU must be USP V/VM or later models and micro-program must be the support version on both sides.
6. For a TC, TCz, or GAD pair with this SOM effective (RI/O MIH time is 5 seconds), the setting of RI/O MIH time made at RCU registration (default is 15 seconds, which can be changed within range from 10 to 100 seconds) is invalid. However, RI/O MIH time displayed on Device Manager - Storage Navigator and CCI is not "5 seconds" but is what set at RI/O registration.
7. If a failure occurs on the switched path between storage systems, Mainframe host MIH or Open server time-out may occur.
8. If an MP to which the path between storage systems belongs is overloaded, switching to an alternate path delays and host MIH or time-out may occur.
9. If an RI/O retry occurs due to other factors than RI/O MIH (5 sec), such as a check condition report issued from RCU to MCU, the RI/O retry is performed on the same path instead of an alternate path. If a response delay to the RI/O occurs constantly on this path due to path failure or link delay, host MIH or time-out may occur due to response time accumulation for each RI/O retried within 5 seconds.
10. Even though this SOM is set to ON, if Mainframe host MIH time or Open host time-out time is set to 10 seconds or less, host MIH or time-out may occur due to a path failure between storage systems.
11. Operation commands are not available for promptly switching to an alternate path.
12. This SOM works for the pair for which initial pair creation or Resync operation is executed.
13. Micro-program downgrade to an unsupported version cannot be executed unless all the TC, TCz, and GAD pairs are suspended or deleted.
14. For operational specifications in each combination of MCU and RCU of TCz/TC, contact customer support (see SOM784 sheet).
15. For GAD pairs, this SOM is effective if the microcode version supports GAD.
16. This SOM does not support iSCSI paths between storage systems. When iSCSI is used for paths between storage systems, the time to switch to an alternate path cannot be reduced. For this, if a failure occurs on a path between storage systems in an environment where host time-out time is short, a time-out may occur on the host side. A time-out may also occur on the host side when a failure occurs on an iSCSI path between storage systems if storage system paths of Fibre and iSCSI coexist in an environment where host time-out time is short so that the configuration where storage system paths of Fibre and iSCSI coexist is not supported too.

Notes:

1. When this SOM is set to ON, the performance characteristic regarding sequential I/Os to the FCv2 target VOL changes.
2. This SOM is applied only when SOM 577 is set to OFF.
3. This SOM is applied if response performance for a host I/O issued to the FCv2 target VOL is prioritized.

Notes:

1. This SOM is applied when:
   • A file system using DP pool VOLs is used.
   • Data Retention Utility is installed.
2. Because the DRU attribute is set to Protect for the V-VOL, read I/Os are also disabled.
3. If Data Retention Utility is not installed, the expected effect cannot be achieved.
4. The Protect attribute of DRU for the DP V-VOL can be released on the Data Retention window of Device Manager - Storage Navigator after recovering the blocked pool VOL.
5. The VVP (Virtual Volume Protection) function when the pool volume is blocked is supported. VVP can be enabled/disabled for each Pool.

   With SOM 803 disabled, VVP when the pool volume is blocked is also disabled by default. But you can enable VVP for each pool whenever you want.

   With SOM 803 enabled, VVP when the pool volume is blocked is also enabled automatically (by default) when you create a new pool.

   Caution: A pool is NOT protected by ANY FUNCTION if you deliberately change VVP for the pool from ON (default) to OFF, even with SOM 803 enabled.

Notes:

1. This SOM is applied when all the following conditions are met
   • ShadowImage is used with SOM 467 set to ON.
   • Write pending rate of an MP unit that has LDEV ownership of the copy target is high
   • Usage rate of a parity group to which the copy target LDEV belongs is low.
   • ShadowImage copy progress is delayed.
2. This SOM is available only when SOM 467 is set to ON.
3. If the workload of the copy target parity group is high, the copy processing may not be improved even if this SOM is set to ON.

Notes:

1. This SOM is applied from factory shipment.
2. Do not change the setting of this SOM during DP-VOL format.
3. If the setting of this SOM is changed during DP-VOL format, the change is not reflected to the format of the DP-VOL being executed but the format continues in the same method.

Notes:

1. To apply this SOM, the RMF version of mainframe z/OS^® to be connected must be 1.12 or higher.
2. If the OS does not use a supported version, the transfer speed cannot be displayed correctly.
3. If all RMF versions of mainframe z/OS connected are 1.12 or higher, set this SOM to ON.
4. If any version of mainframe z/OS connected is lower than 1.12, set this SOM to OFF.

Notes:

1. This SOM is applied when you need to disable the background format for a DP/DT/TI pool due to a concern of performance degradation of other functions in an environment where a DP-VOL is used by other functions.
2. When the background format function is enabled, because up to 42 MB/s of ECCG performance is used, local copy performance may degrade by about 10%. Therefore, confirm whether the 10% performance degradation is acceptable or not before enabling the function.
3. When a Dynamic Provisioning VOL on an external storage system, which is used as an external VOL, is used as a pool VOL, if the external pool on the external storage side becomes full due to the background format, the external VOL may be blocked.

   If the external pool capacity is smaller than the external VOL capacity (Dynamic Provisioning VOL of external storage system), do not enable the background format function.

4. When a Dynamic Provisioning VOL on an external storage system, which is used as an external VOL, is used as a pool VOL, if the external pool on the external storage side becomes full due to the background format, the external VOL may be blocked.

   If the external pool capacity is smaller than the external VOL capacity (Dynamic Provisioning VOL of external storage system), do not enable the background format function.

5. If the background format function is disabled by changing this SOM setting, the format progress is initialized and the entire area becomes unformatted.
6. This SOM is set to ON before shipment.

Mode 899 = ON (default):

• SOM 900 is ON: I/O synchronous copy starts without retrying Volume Migration.
• SOM 900 is OFF: I/O synchronous copy starts when the threshold of Volume Migration retry is  exceeded. (Recommended)

Mode 899 = OFF:

• SOM 900 is ON: I/O synchronous copy starts when the number of retries reaches half of the threshold of Volume Migration retry.
• SOM 900 is OFF: Volume Migration is retired and I/O synchronous copy is not executed.

Notes:

1. This SOM is applied when improvement of Volume Migration success rate is desired under the condition that there are many updates to a migration source volume of Volume Migration.
2. During I/O synchronous copy, host I/O performance degrades.

Mode 900 = ON:

• SOM 899 is ON: I/O synchronous copy starts without retrying Volume Migration.
• SOM 899 is OFF: I/O synchronous copy starts when the number of retries reaches half of the threshold of Volume Migration retry.

Mode 900 = OFF (default):

• SOM 899 is ON: I/O synchronous copy starts when the threshold of Volume Migration retry is exceeded. (Recommended)
• SOM 899 is OFF: Volume Migration is retired and I/O synchronous copy is not executed.

Notes:

1. This SOM is applied when improvement of Volume Migration success rate is desired under the condition that there are many updates to a migration source volume of Volume Migration.
2. During I/O synchronous copy, host I/O performance degrades.

Notes:

1. This SOM is applied when pages with the maximum capacity need to be allocated to tier1 (drive type is SSD) with Dynamic Tiering or Dynamic Tiering for Mainframe.
2. When Tier1 is SSD while SOM 901 is set to ON, the effect of SOM 897 and 898 to the gray zone of Tier1 and Tier2 is disabled and the SOM 901 setting is enabled instead. In addition, the settings of SOM 897 and 898 are effective for Tier2 and Tier3.
3. The following is recommended when applying SOM 901:

   [actual I/O value (total number of I/Os of all tiering policies)] < [performance potential value of Tier1* × 0.6]

   * The performance potential value of Tier1 displayed on Monitor information by using Dx-ray. For details, contact customer support (see SOM897_898_901 sheet).

Notes:

1. This SOM is applied when:
   • Dynamic Tiering for Mainframe is used (including multi-platform configuration).
   • The requirement for response time is severe.
2. The number of pages to be migrated per unit time at tier relocation decreases.

Notes:

1. If a CLPR is used by only some MPBs among all the installed MPBs, set this SOM to ON for the CLPR to increase CM capacity allocated to the MPBs that use the CLPR.

   Example:

   (a) A CLPR only for UR JNLG.

   (b) A configuration where MPBs and CLPRs are separately used for Open and Mainframe systems.

2. Since CM capacity allocated to MPBs with low load is small, the performance is affected by a sudden increase in load.
3. SOM 908 cannot be used with SOM 933. When SOM 933 is set to ON, the function of SOM 908 is canceled even though SOM 908 is ON.
4. This SOM is effective for a CLPR. Therefore, when setting this SOM to ON/OFF, select target "LPRXX (XX=00 to 31)". For example, even when CLPR0 is defined (any of CLPR1 to 31 are not defined), select "LPR00" first and then set this SOM to ON/OFF.

Notes:

1. This SOM is applied when stopping or disabling zero data page reclamation by user request is required.
2. When this SOM is set to ON, the zero data page reclamation does not work at all.

   * Zero data page reclamation by WriteSame and UNMAP, IO synchronous page reclamation, program product synchronous page reclamation, and UDSR page reclamation can work.

3. When downgrading micro-program to a version that does not support this SOM while this SOM is set to ON, set this SOM to OFF after the downgrade.

   * Because the zero data page reclamation does not work at all while this SOM is set to ON.

4. This SOM is related to SOM 755 and SOM 859. For relationship with SOM755 and SOM859, contact customer support (see SOM930 sheet).

Notes:

1. This SOM is applied when HDT monitoring data collection is required in DP environment.
2. When HDT is already used, do not set this SOM to ON.
3. For HDT monitoring data collection, shared memory for HDT must be installed. For details, contact customer support (see SOM937 sheet).
4. If monitoring data collection is performed without shared memory for HDT installed, an error is reported and the monitoring data collection fails.
5. Before removing the shared memory for HDT, set this SOM to OFF and wait for 30 minutes.
6. Tier relocation with monitoring data collected when this SOM is set to ON is disabled.
7. When DP is converted into HDT (after purchase of software license), the collected monitoring data is discarded.
8. Before downgrading the micro-program to an unsupported version, set SOM 937 to OFF and wait for at least 30 minutes.

Mode 972 = OFF (default):

• When SOM 972 and SOM 973 are both OFF, the THP page size is 0x15000 (42MB).
• When SOM 972 is OFF and SOM 973 is ON, the THP page size is 0x10 (8KB).

Notes:

1. This SOM is applied when a delay in host I/O response due to reclamation processing occurs in a customer environment.
2. Reclamation processing is delayed.
3. This SOM is to prioritize host I/O response over reclamation processing in VxVM environment, so that the time required for reclamation processing may increase when this SOM is set to ON.

Notes:

1. This SOM is applied when a delay in host I/O response due to reclamation processing occurs in a customer environment.
2. When this SOM is set to ON, reclamation processing is delayed.
3. This SOM is to prioritize host I/O response over reclamation processing in VxVM environment, so that the time required for reclamation processing may increase when this SOM is set to ON.

Notes:

1. This SOM is applied when the auto-recovery of external volumes that are blocked due to Not Ready status is desired in UVM connection using an ECM storage system as an external storage system.
2. When this SOM is set to ON and the connected external storage system is not in stable status (such as failure and recovery from failure), a blockage due to Not Ready status and auto-recovery might occur repeatedly.

Notes:

1. This SOM applies when one of the following conditions is met:
   1. Multiple journals are registered in a consistency group of CCI.
   2. Multiple journals are registered in an extended consistency group.
   3. Journals are accumulated at the secondary site, causing the system performance to decrease.
2. If SOM 690 is set to ON and the Write Pending rate is 60% or higher, the journal copy is disabled regardless of the setting of this SOM.
3. When the host write speed is faster than the JNL copy speed, the usage rate of the master journal increases.
4. This SOM is effective within the range of each CLPR. Therefore, an operation target LPRxx (xx= 00 to 31) needs to be selected before setting this SOM to ON/OFF.

   For example, when setting this SOM only to CLPR0 (even though this SOM is not set to CLPR 1 to 31), select "LPR00" and then set this SOM to ON/OFF. If "System" is selected and then this SOM is set to ON, this SOM is not effective for any of the CLPRs.

5. Set SOM 1043 to ON when journals are not accumulated at the RCU. If journals have already been accumulated at the RCU, journal copy does not start until the journal usage rate becomes 0%. (If you need to set SOM 1043 to ON while journals are accumulated, set Purge Suspend, and then perform resync.)

Notes:

1. This SOM is applied when the CAW function is enabled.
2. The cache write pending rate may increase.

Notes:

1. This SOM is applied to enable microcode downgrade to a version that does not support URxUR (including delta) if the configuration where any UR pair has been registered is not URxUR (including delta).
2. Setting this SOM to ON allows microcode downgrade at sites where only 1 mirror is used in URxUR multi-target configuration without delta resync and cascade configuration (L or R site in multi-target, and P or R site in cascade), but the following phenomena occur after microcode downgrade. Make sure that the target storage system does not contain pairs of URxUR configuration.
   Phenomena:

   1. When the microcode is downgraded at S site (local or remote) in multi-target configuration, the pair between P site and the target S site cannot be resynchronized.
   2. When the pair between I site and R site in cascade configuration is resynchronized, the pair status cannot change from COPY to PAIR.
   3. When the microcode is downgraded at R site in cascade configuration, the pair between I site and R site cannot be resynchronized.

Notes:

1. Apply this mode to detect a minor delay in drive response.
2. When a delay is suspected, a processing to refer to the statistics data and determine the delay works.
3. If SOM 157 is set to ON, the output prevention status of SSB=A4CE is not cleared in one-day cycle.
4. When applying this SOM only, a SIM for delay detection is reported but the drive is not blocked. To block the drive, SOM 144 also needs to be applied.

Notes:

1. This SOM is applied when the page problem occurs in an environment where Symantec ASL 6.0.5 or higher is used and SOM 972 and/or 973 is set to ON.
2. When this SOM is set to ON, reclamation processing is delayed.
3. The priority of setting when SOMs are set at the same time is SOM 1069, SOM 972, and then SOM 973. The setting of higher priority SOM is enabled.

Notes:

1. This SOM is applied when reducing the time to complete status change of all pairs in a consistency group at a group operation (suspension and resync operation) with the GAD CTG function. In a system configuration where host I/O performance is prioritized, do not use this SOM because setting this SOM may affect the host I/O performance.
2. The MP usage rate increases during status change of all pairs in a consistency group. For details about approximate percentage increase in MP usage rate, contact customer support (see SOM1070 sheet).

Notes:

1. The mode is applied if avoiding impacts on commands for other external devices that share a Target port on an external system side with a quorum disk is prioritized over preventing quorum disk blockage when a response to ABTS is delayed due to path performance degradation in a configuration where the Target port is shared between external devices and the quorum disk.
2. When connection performance degradation occurs, the quorum disk blockage is more likely to occur.

Notes:

1. This SOM is applied when the following conditions are met.
   • A DP-VOL with data direct mapping attribute is deleted.
   • The data of external volume with data direct mapping attribute associated with a deletion target DP-VOL with data direct mapping attribute will not be used again.
2. When SOM 1083 is set to ON, the data of external volumes cannot be guaranteed.
3. When DP-VOL deletion is performed without disconnecting an external volume, the data of the external volume cannot be guaranteed.

Notes:

1. This SOM is applied when the IOPS performance of an external storage system is higher than 80k × the number of installed MPBs, which is the value of IOPS that an entire local storage system sends to an external storage system.
2. When it is required to set this SOM to OFF, if IOPS sent from the local storage system to the external storage system is higher than 80k × the number of installed MPBs, reduce the IOPS to lower than 80k × the number of installed MPBs, and then set this SOM to OFF. (Otherwise CWP increases and cache is overloaded.)

Notes:

1. This SOM can be applied when DKCMAIN version that supports the zHyperWrite function is used.
2. To use the zHyperWrite function, a HyperSwap environment is required.
3. To enable the zHyperWrite function, set this SOM to ON on both MCU and RCU of TCz.
4. To downgrade the microcode to a version that does not support the zHyperWrite function, set this SOM to OFF prior to downgrading the microcode.
5. Even when this SOM is set to ON for a storage system in 3DC configuration, the zHyperWrite function does not work for volumes in 3DC configuration.

   However, if the mode is set to ON and the zHyperWrite + 3DC multiple-target option is enabled, the zHyperWrite function works in TCz-URz multi-target configurations.

6. Do not set this SOM to ON if SOM 474 is set to ON.
7. Do not set this SOM to ON if Preserve Mirror configuration is created.
8. Do not set this SOM to ON if the TCz Function Switch 12 is set to ON.
9. To use the zHyperWrite function, do not select Primary Volume Only as a CFW Data option at TCz pair creation.

Notes:

1. This SOM is applied when downgrading microcode from a version that supports pool reduction rate correction to a version that does not support the function is disabled.
2. When pool capacity shrinking is performed for an FMD parity group while the mode is set to ON, the pool capacity shrinking cannot be completed. Make sure to set the mode to OFF prior to performing pool capacity shrinking for an FMD parity group.

Notes:

1. This SOM is applied when a significant delay, which is about 200 msec or longer, occurs in the line between MCU and RCU.
2. When this SOM is set to ON while round-trip delay time is small (about less than 20 msec), the usage rate of RCU Initiator increases by 10% x the number of journals.
3. Even though this SOM is supposed to be applied to UR RCU, apply it to both MCU and RCU on the premise of DR operation.
4. This SOM is effective for each CLPR, so that select the operation target LPRxx (xx=00 to 31), and then set this SOM to ON/OFF. For example, when only CLPR0 is defined (CLPR1 to 31 are not defined), select LPR00 and then set this SOM to ON/OFF. This SOM is not effective for any CLPRs if "System" is selected even when this SOM is set to ON.

Mode 1099 = ON: When FREEZE is received, the completion of path deletion for those other than the last path is not reported but only the completion of path deletion for the last path is reported. If multiple CUs share an RCU path, path deletion does not work at FREEZE per CU, so that the following phenomenon may occur:

• After Hyperswap is performed, SSB=8BD8 and 8BD9 are logged for a pair where the Hyperswap is performed.

Notes:

1. Apply this SOM when a storage system with over 32 CUs is used in a TCz environment in which PPRC FREEZE is available.
2. To use 32 more CUs in GDPS environment, the microcode must be the supported version on both MCU and RCU and this SOM is set to ON.

Mode 1106 = ON: The rebalance (the same as the rebalance that works at pool expansion or after 0 data page reclamation) (*3) works when one of the following conditions is met:

1. The usage rate is checked for parity groups in a pool once a day, and the usage rate is not balanced (*1) among parity groups.
2. After 0 data page reclamation, the number of reclaimed pages is 0 (*2).

Examples:

1. In an HDP pool, if the usage rates of PG1, PG2, and PG3 are 50%, 40%, and 30% respectively, it is not determined as unbalanced.

   Because the average parity group usage rate is (50%＋40%＋30%) / 3 ＝40% and the difference in the rate between each parity group and the average is 10% at the maximum.

2. In an HDP pool, if the usage rates of PG1, PG2, and PG3 are 80%, 40%, and 30% respectively, it is determined as unbalanced.

   Because the average parity group usage rate is (80%＋40%＋30%) / 3 ＝50% and the difference in the rate between each parity group and the average is 30% at the maximum.

3. In an HDT pool, if the usage rates of PG1, PG2, and PG3 are 80% (SSD), 40% (SAS15K) and 30% (SAS15K), it is not determined as unbalanced, because:
   • The average parity group usage rate of Tier1 is (80%) / 1 ＝80% and the difference in the rate between the parity group and the average is 0%.
   • The average parity group usage rate of Tier2 is (40%＋30%) / 2 ＝35% and the difference in the rate between the parity group and the average is 5% at the maximum.

Notes:

1. This SOM is applied when balancing the usage rate is required at a customer site where the usage rate is not even.
2. The term "page usage rate" refers to the percentage of the number of assigned pages in each PG compared to the total number of pages in the pool.

   For HDT pools, the term "total number of pages" is the number of pages assigned within each specific tier.

Mode 1115 = OFF: When LDEV format is performed for a virtual volume with capacity saving enabled, normal formatting is performed, but if one of the following conditions is met, the data is initialized without using metadata.

• There is a pinned slot.
• The capacity saving status is "Failed".
• The virtual volume is blocked (Normal restore cannot be performed).

The processing time increases with increase in pool capacity. Estimate of processing time:

Processing time (minutes) = (pool capacity (TB)/40) + 5 

* To reduce the capacity consumption in the case that the pool capacity is almost depleted for example, the deduplication processing might be performed during the resync processing. In particular, the following cases apply:

• The usage rate exceeds the warning threshold.
• Free capacity is smaller than about 240 GB.

Notes:

1. When SOM 1280 is ON, deduplication processing is performed even when SOM 1169 is ON.
2. If conditions to disable deduplication processing by SOM 1191 are met, deduplication processing is not performed even when SOM 1169 is OFF. For details about the conditions to disable deduplication processing, contact customer support (see SOM1191 sheet).
3. When SOM 1169 is set to ON, like the post mode, estimating and reserving the capacity of a temporary storing area in the copy target DP volume or pool in advance is necessary.
4. SOM 1169 is not effective for the initial copy at pair creation, but there are some exceptional cases for SI and VM, such as pair creation using a used volume for S-VOL. In this case, deduplication processing is performed or not performed according to the mode setting.
5. SOM 1169 is not related to determining whether to perform deduplication processing in synchronization with initial write. For example, the setting of SOM 1169 does not contribute to a reduction in time to migrate data to a newly defined volume.

Notes:

1. Apply SOM 1174 when discovery is performed while specifying a universal port that is being logged in from a host or an external storage system.
2. If SOM 1174 is set to ON, external volumes cannot be created using the paths being logged in from hosts and external storage systems.
3. When WWN discovery is performed while the mode is set to ON, the storage system being logged in from hosts and external storage systems are displayed as [Unknown] in the discovery result.
   Discovery works at the following operations or commands:

   • HDvM - SN: External volume addition, external path setting change
   • CCI: raidcom add external_grp, raidcom add path, raidcom discover external_storage, raidcom discover lun
4. By specifying the -safety_check enable option for the above CCI commands, path disconnection can be prevented same as the case of setting the mode to ON. The option is supported with 90-06-01-00/00 and later and CCI 01-61-03/xx and later. For details, see Command Control Interface Command Reference.

Notes:

1. Apply the mode if the CFW data transfer from the URz P-VOL to the S-VOL is required. When a pair is created with the mode set to ON, the CFW data that the P-VOL receives is transferred to the S-VOL. It can apply to pair creation from BCM or CCI only. If a pair is created from Device Manager - Storage Navigator, whether to transfer the CFW data can be selected as usual.
2. To transfer the CFW data to the S-VOL, a journal creation is performed as an extension of CFW write, which causes the CFW write performance to degrade compared to that when the mode is set to ON.
3. The mode setting (ON/OFF) can be changed regardless of the URz pair status, but to transfer the CFW data to the S-VOL, a new pair must be created after setting the mode to ON.

Notes:

1. This SOM is applied when reducing impact on I/O performance is required at online data migration for a virtual volume with capacity saving enabled and the inline mode set.
2. If this SOM is set to ON, the frequency of the asynchronous deduplication processing increases after storing the data in a temporary area so that the pool capacity decreases due to consumption of the temporary area. To use the mode therefore, decrease in pool capacity must be acceptable. In particular, verify the capacity of the temporary area in the pool by using the following conditional expressions.

   <Setting the mode at data migration>

   [Pool capacity × depletion threshold (%) / 100] is larger than [current used pool capacity + (amount of data to be migrated × (100 – estimated compression ratio (%)(*)) / 100)].

   <Setting the mode during normal operation>

   [Pool capacity × depletion threshold (%) / 100] is larger than [current used pool capacity + (amount of data to be written to area without having been written × (100 – estimated compression ratio (%)(*)) / 100)].

   * Estimated compression ratio is the ratio of the estimated compression reduction effect. To convert the compression ratio in N:1 format to percentage, use the formula: compression ratio (%) = (1 – 1 / N) × 100

3. To set the mode to ON, first estimate temporary area in a pool and then reserve it in advance.
4. By setting the mode to ON, the inline deduplication processing is disabled when the average MP usage is 50% or higher even though SOM 1280 is set to ON.
5. When SOM 1169 is set to ON, the inline deduplication at copy processing is disabled regardless of SOM 1191 setting.
6. For conditions to stop deduplication processing according to the setting combination of SOMs 1191, 1247, and 1248, contact customer support (see the SOM1191 sheet).

Mode 1198 = OFF (default):

• When SOM 1198 is OFF and SOM 1199 is ON, the difference management method for volumes of 4 TB or less used in TC, UR, or GAD pairs is changed to SM difference management.
• When both SOM 1198 and SOM 1199 are OFF, the difference management method is not changed.

Notes:

1. Changing the difference management method can affect the I/O response performance depending on the I/O pattern.
2. Changing the difference management method can affect the initial copy time depending on the conditions.

Mode 1199 = ON:

• When both SOM 1199 and SOM 1198 are ON, the difference management method for volumes of 4 TB or less used in TC, UR, or GAD pairs is changed to hierarchical difference management regardless of SOM 5 and 6 settings.
• When SOM 1199 is ON and SOM 1198 is OFF, the difference management method for volumes of 4 TB or less used in TC, UR, or GAD pairs is changed to SM difference management regardless of SOM 5 and 6 settings.

Mode 1199 = OFF (default):

• When SOM 1199 is OFF and SOM 1198 is ON, the difference management method for volumes of 4 TB or less used in TC, UR, or GAD pairs is changed to hierarchical difference management regardless of SOM 5 and 6 settings.
• When both SOM 1199 and SOM 1198 are OFF, the difference management method is not changed.

Notes:

1. The SOM is applied to enable users who use CCI in TC, UR, and GAD operations to switch difference management method from hierarchy difference management to SM difference management for volumes of 4TB or less used in TC/UR/GAD pairs.
2. Changing the difference management method can affect the I/O response performance depending on the I/O pattern.
3. Changing the difference management method can affect the initial copy time depending on the conditions.

Mode 1202 = ON:

• Synchronous read I/Os are disabled.
• Read I/Os other than synchronous read are disabled.
• Write I/Os are disabled.

Mode 1202 = OFF (default):

• Synchronous read I/Os can be done by collection read.
• Read I/Os other than synchronous read are disabled.
• Write: I/Os are disabled.

Notes:

1. Apply this mode when changing the behavior back to the previous one is required during FMD and SSD firmware replacement.
2. When this mode is set to ON, the host I/O performance during FMD or SSD drive firmware replacement may be degraded.

Notes:

1. The mode is applied to prevent the host response performance from being degraded due to background unmap.
2. When SOM 1122 is set to ON, the SOM 1122 setting is prioritized.
3. As releasing physical areas runs at the normal speed, the following phenomena may occur, though the phenomena are solved immediately after the physical area release is complete:
   • The used pool capacity does not decrease immediately after DP volume deletion.
   • The saving ratio seems to be lower temporarily.
   • The used pool capacity may increase due to rebalance.

Journal data copy is disabled when the following conditions (1) and (2), or (1) and (3) are met:

1. 4096 or more journal data sets are accumulated on RCU.
2. The write pending rate of a journal volume in an MPB that has the ownership of the journal on RCU exceeds the threshold, 25% (mode OFF) or 50% (mode ON). (Including the write pending rate of those other than the journal volume)
3. On RCU, it takes 15 seconds or longer to start a restore operation after the copy processing of journals is complete.

Notes:

1. Apply this SOM when one of the following conditions are met:
   1. Disabling journal data copy is enabled in one of the following cases:

      - SOM 1043 is set to ON for each CLPR on the secondary site.

      - A configuration where multiple journals are added to a CCI consistency group (open and mainframe).

      - A configuration where multiple journals are added to an extended consistency group (mainframe).

   2. The write pending rate of a CLPR containing a journal on the secondary site exceeds 25%.
2. If the host write I/O speed is faster than the journal data copy speed, the usage of the master journal increases.
3. Though the mode can work on UR/URz RCU, apply it to both MCU and RCU assuming Disaster Recovery operation.
4. This mode is related to SOM 1043.
5. If SOM 690 is set to ON and the write pending rate is 60% or higher, journal data copy is disabled regardless of the setting of this mode.
6. This mode is effective per CLPR. Therefore, select a target LPR xx (xx= 00 to 31), and then set the mode to ON or OFF. For example, when setting the mode to CLPR0 (CLPR 1 to 31 are not defined), select LPR00, and then set the mode to ON or OFF. When setting the mode by selecting System, the mode cannot be enabled for any CLPRs.

* Different from other program products, the ownership in an MPU with the journal group ownership is migrated as follows in a UR/URz configuration.

• Ownership migration target: LDEV (journal volume, remote CMDDEV)
• Timing when ownership migration takes place: Journal volume deletion, journal group deletion from EXCTG, and mirror allocation release

Notes:

1. Apply the mode when preventing the MP usage rate increase is required.
2. Ownerships are in a specific MPU so that I/Os may be concentrated on the MPU.
3. Ownership migration does not work at pair deletion.

Mode 1254 = ON:

• SI/SIz, VM, HTI, TC/TCz, GAD, UR/URz: The copy processing running in the background* stops when the WP rate of the copy target CLPR is 35% or higher.
• FC: The pace of the copy processing running in the background* is slowed down when the WP rate of the copy target CLPR is 35% or higher.

Mode 1254 = OFF (default):

• SI/SIz, VM, FC, TI: As per the SOM 467 setting
• TC/TCz, GAD: As per the SOM 689 setting
• UR/URz: As per the SOM 690 setting

Notes:

1. Apply this mode when all the following conditions are met:
   1. Preventing the performance of a host write I/O to a DRD-VOL from being degraded due to overload by the copy processing running in the background is required.
   2. It is acceptable that completing the copy processing running in the background for a volume (*1) belonging to a CLPR whose WP rate is 35% or higher takes extra time equal to the time period during which the WP rate of the copy target CLPR is 35% or higher.
   3. Setting the mode for all CLPRs on the storage system is required. (For per CLPR setting, use SOM 1260.)
   4. A failure suspension of a UR/URz pair is acceptable (*2)(*3). The failure suspension occurs when the mode is set to ON to prioritize the host I/O performance in a UR/URz configuration, if the amount of host I/Os exceeds the amount of journal transfer so that the journal usage increases, and then the journal usage exceeds the threshold.

   *1: Note that in CLPRs with the mode set to ON, the copy processing does not make progress for not only a DRD-VOL but also a normal volume and a virtual volume with capacity saving disabled.

   *2: Disable Inflow Control for journals. By setting SOM 1254, the copy processing running in the background is stopped, the amount of host I/Os exceeds the amount of journal transfer, and the journal usage increases. If Inflow Control is enabled, failure suspension can be prevented, but Inflow Control works when the journal usage exceeds the threshold (80%), resulting in host write performance degradation.

   *3: If a failure suspension is not acceptable, use different CLPRs for the UR/URz S-VOL and JNL VOL, and for the DRD-VOL whose performance cannot be degraded on RCU, and then set SOM 1260 to ON only f+F97or the CLPR of the DRD-VOL whose performance cannot be degraded.

2. By setting the mode to ON, the copy processing running in the background is stopped when the WP rate is 35% or higher regardless of the settings of SOM 467, SOM 689, and SOM 690.
3. Completing the copy processing running in the background for a volume (*4) belonging to a CLPR whose WP rate is 35% or higher takes extra time equal to the time period during which the WP rate of the copy target CLPR is 35% or higher. Note that recovering a pair that is suspended due to failure takes longer time too. SOM 1254 cannot be applied if the copy processing, such as the case of data migration or volume migration, must be completed in a certain time period.

   *4: Note that in CLPRs with the mode set to ON, the copy processing does not make progress for not only a DRD-VOL but also normal volume and virtual volume with capacity saving disabled.

4. When UR/URz is used, if 35% or higher WP rate continues for a long time on RCU, a journal volume becomes full and may be suspended on MCU.

   To disable the copy running in the background of replication program products other than UR/URz, do not set the mode to ON.

   Instead of setting the mode to ON, use different CLPRs for the UR/URz S-VOL and the journal volume, and for the DRD-VOL for which preventing performance degradation is required on RCU, and set SOM 1260 to ON for the CLPR of the DRD-VOL only.

5. In a 3DC configuration, if 35% or higher WP rate continues for a long time on the second RCU, a journal volume becomes full and may be suspended on MCU and the first RCU. In this case, even if you perform delta resync, all data copy from P-VOL to S-VOL works same as the case when delta resync fails.
6. In a UR M:N open CTG configuration, even if there is one storage system where the WP rate reaches 35% or higher on RCU, copy processing will be stopped on all storage systems in this configuration, including the storage systems with SOM 1254 disabled.
7. In a URz EXCTG configuration, even if there is one storage system where the WP rate reaches 35% or higher on RCU, copy processing will be stopped on all storage systems in this EXCTG, including the storage systems with SOM 1254 disabled.
8. Apply the same setting of SOM1260 for the CLPR of UR/URz S-VOL and the CLPR of the journal volume.

   (Set the mode to ON or OFF for both CLPRs)

9. When UR/URz is used, if operations are switched to RCU, as the previous MCU becomes RCU, meet the following conditions:
   1. The SOM setting is same for MCU and RCU.
   2. If different CLPRs are used for the UR/URz S-VOL and the journal volume, and for a DRD-VOL for which preventing performance degradation is required on RCU, use different CLPRs for the UR/URz S-VOL and the journal volume, and for a DRD-VOL for which preventing performance degradation is required on MCU too.
10. In a 3DC configuration, because operations on MCU can be switched to the first RCU or the second RCU, make sure the SOM setting is the same on the MCU, the first RCU and the second RCU.
11. When UR/URz is used, disable Inflow Control. If enabled, it may work because the copy is stopped by setting the mode to ON, resulting in degradation of host write I/O performance.

Notes:

1. Apply the mode when all the following conditions are met.
   • Preventing the performance of a host write I/O to a DRD-VOL from being degraded due to overload by the background copy processing is required.
   • It is acceptable that completing the background copy for a volume (*1) belonging to a CLPR whose WP rate is 35% or higher takes extra time equal to the time period during which the WP rate of the copy target CLPR is 35% or higher.
   • Setting the mode per CLPR is required. (Setting for all CLPRs, use SOM 1254)
   • The mode setting for a CLPR of UR/URz S/VOL, and that for a CLPR of a journal volume are the same. (The mode is set to ON or OFF for both CLPRs)
   • *1: Note that in CLPRs with the mode set to ON, the copy processing does not make progress for not only a DRD-VOL but also a normal volume and a virtual volume with capacity saving disabled.
2. By setting the mode to ON, the copy processing running in the background is stopped when the WP rate is 35% or higher regardless of the settings of SOM 467, SOM 689, and SOM 690.
3. Completing the copy processing running in the background for a volume (*2) belonging to a CLPR whose WP rate is 35% or higher takes extra time equal to the time period during which the WP rate of the copy target CLPR is 35%. Note that recovering a pair that is suspended due to failure takes longer time too.

   *2: Note that in CLPRs with the mode set to ON, the copy processing does not make progress for not only a DRD-VOL but also normal volume and virtual volume with capacity saving disabled.

4. When UR/URz is used, if 35% or higher WP rate continues for a long time on RCU, a journal volume becomes full and may be suspended on MCU.

   To disable the background copy of replication program products other than UR/URz, use different CLPRs for the UR/URz S-VOL and the journal volume, and for a DRD-VOL for which preventing performance degradation is required on RCU, and set the mode to ON for the CLPR of the DRD-VOL only.

5. When UR/URz is used, if operations are switched to RCU, as the previous MCU becomes RCU, meet the following conditions:
   • The SOM setting is same for MCU and RCU.
   • If different CLPRs are used for theUR/URz S-VOL and the journal volume, and for a DRD-VOL for which preventing performance degradation is required on RCU, use different CLPRs for the UR/URz S-VOL and the journal volume, and for a DRD-VOL for which preventing performance degradation is required on MCU too.

Asynchronous processing that runs at low speed by setting the mode to ON:

• Disabling of the capacity saving function
• Deletion of LDEVs for which the capacity saving function is enabled
• Garbage collection
• Asynchronous capacity reduction processing
• Compression conversion of compression accelerator
• Garbage collection for collecting unnecessary meta data or user data of deduplication system data volume (data store)
• Deletion of unnecessary hash data for deduplication
• Expansion of meta data area of the capacity saving
• Correction of control information when SOM 1208 is set to ON
• Health check when SOM 1237 is set to ON

Notes:

1. Apply this mode in the following cases:
   • There is a possibility of drive overload by the asynchronous processing (asynchronous capacity reduction, disabling capacity saving, compression conversion of compression accelerator) that works after the data reduction setting (capacity saving, compression accelerator) is changed.
   • The drive is overloaded by asynchronous processing of capacity saving.
2. By setting the mode to ON, the capacity saving ratio may decrease.
3. When an adaptive data reduction setting change is complete after setting the mode to ON, set the mode to OFF.