System option modes

Notes:

1. This SOM is used on a storage system where slow or delayed drive response 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).

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. This SOM is effective for the entire storage system.

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 is determined is shorter than usual.

Notes:

1. The mode is applied when a user requires to suspend the pair one minute after a communication error between UR MCU and RCU is detected.
2. When SOM 449 is set to ON, SOM 448 does not function.

Notes:

1. This SOM is applied when disabling the detection of communication failures between the MCU and RCU in UR configuration is required.
2. When this SOM is set to ON, SOM 448 does not work.
3. This SOM setting is not changed by microcode upgrade.
4. This SOM is not effective for remote paths between an Initiator port on the MCU and a Target port on the RCU.
5. While a path from the RCU to MCU is disconnected, if the UR pair remains in Suspending or Deleting status, recover it in accordance with the procedure in Recovery from UR Failure in TROUBLE SHOOTING section of Maintenance Manual.

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. 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.
   • 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.

Mode 506 = ON:

• 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. 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 higher on the RCU for a long time, it takes extra time for the initial copy and resync copy to be completed due to the slower 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.

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 an 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 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.

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. Mode 757 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 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 and GAD pairs on the storage system, unable to specify the pairs that are using this function or not.
5. For a TC 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.
6. If a failure occurs on the switched path between storage systems, Mainframe host MIH or Open server time-out may occur.
7. 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.
8. 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.
9. 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.
10. Operation commands are not available for promptly switching to an alternate path.
11. This SOM works for the pair for which initial pair creation or Resync operation is executed.
12. Micro-program downgrade to an unsupported version cannot be executed unless all the TC and GAD pairs are suspended or deleted.
13. For operational specifications in each combination of MCU and RCU of TC, contact customer support (see SOM784 sheet).
14. For GAD pairs, this SOM is effective if the microcode version supports GAD.
15. 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. 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, a read I/O is 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 Virtual Volume Protection (VVP) function can be enabled/disabled for each pool. With SOM 803 disabled, VVP is also disabled by default, but you can enable VVP for each pool as needed. With SOM 803 enabled, VVP is also enabled automatically (by default) when you create a new pool. Caution: A pool is NOT protected by ANY FUNCTION if you deliberately turn 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. 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. If the background format function is disabled by changing this SOM setting, the format progress is initialized and the entire area becomes unformatted.

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.
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.

Notes:

1. This SOM is applied when 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. When the mode is set to ON, zero data page reclamation by WriteSame function, UNMAP function, I/O synchronous page reclamation, program product synchronous page reclamation, and UDSR page reclamation can work.
5. This SOM is related to SOM 755.

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.

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.

For VSP G/F350, G/F370, G/F700, G/F900, the following conditions (1) and (2) or (1) and (3) are met:

1. 4,096 or more journals are accumulated at the secondary site.
2. The CLPR write pending rate for journal volumes of MP unit for which journal ownership at the RCU is defined is 25% or higher (including the write pending rate for other than journal volumes).
3. The initiator operating rate of the MP unit for which journal ownership at the RCU is defined is 40% or higher.

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 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 mode only, a SIM for delay detection is reported but the HDD is not blocked. To block the HDD, 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, 972, and then 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. This SOM is applied if avoiding impacts on commands for other external devices sharing 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.

   The delay is caused 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 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 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 (VSP E series) or when the following condition (1) is met (VSP G130, G/F350, G/F370, G/F700, G/F900):

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.

Mode 1115 = OFF (default): 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. If WWN discovery is performed while SOM 1174 is set to ON, the storage system being logged in from hosts and external storage systems are displayed as [Unknown] in the discovery result.

Notes:

1. Before setting this mode to ON, estimate the temporary area in a pool and then reserve it in advance. For details, see the Caution* below.
2. 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.
3. When SOM 1169 is set to ON, the inline deduplication at copy processing is disabled regardless of SOM 1191 setting.

* Caution: When SOM 1191 is ON and MP usage (entire storage system) reaches or exceeds 50%, the pool used capacity increases due to consumption of temporary area for post-process deduplication processing. Before enabling this SOM, verify that there is enough pool capacity by using the following conditional expressions, and then set SOM 1191 to ON only when the applicable conditional expression is met:

• If SOM 1191 is set to ON during data migration:

  pool-capacity × depletion-threshold [%] / 100 > current-pool-used-capacity
  ＋ (data-capacity-to-be-migrated × (100 - estimated-compression-ratio
  [%]*) / 100)

• If SOM 1191 is set to ON during normal operations:

  pool-capacity × depletion-threshold [%] / 100 > current-pool-used-capacity
  ＋ (data-capacity-to-be-written-to-non-write-area × (100 - estimated-compression-ratio [%]*) / 100)

compression-ratio [%] = (1 - 1 ÷ N) × 100

Mode 1198 = OFF:

• 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. Apply this mode when the storage system does not have an SVP and you want to expand the capacity of volumes used in TC, UR, or 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 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:

• 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. Apply this mode when the storage system does not have an SVP and you want to expand the capacity of volumes used in TC, UR, or 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/O: Disabled.
• Other than synchronous read I/O: Disabled.
• Write I/O: Disabled.

Mode 1202 = OFF:

• Correction read: Enabled.
• Other than synchronous read I/O: Disabled.
• Write I/O: Disabled.

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.

Apply this mode when all of the following conditions are met:

1. Disabling journal data copy is enabled by meeting one of the following conditions:

   SOM1043 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).

2. The write pending rate of a CLPR containing a journal on the secondary site exceeds 25%.

Notes:

1. Though the mode can work on UR/URz RCU, apply it to both MCU and RCU assuming Disaster Recovery operation.
2. This mode is related to SOM 1043.
3. 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.
4. 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.

Notes:

1. Apply the mode when all the following conditions are met:
   1. The microcode that supports the mode is applied.(93-04-01 and later, 88-07-03 and later)
   2. The response time of Write Same command increase about 0.1 msec.
   3. The length of Write Same command is short. (less than 256KiB)
2. The mode is effective for the entire storage system.

Different from other program products, the ownership in an MPU with the journal group ownership is migrated as follows in a UR 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. The mode is effective for the entire storage system.