Advantages
The ODM updates enable the AIX® system to recognize Hitachi disk devices and set the proper attributes. If the attributes for queue type, queue depth, and read/write timeout are not the same for all Hitachi devices, disk errors can be logged both on the storage system and in the AIX® error log.
If the ODM update is installed and a device is discovered, a match will be found in the ODM, and the attributes will be set to the default values recommended by the manufacturer. For disk devices, the default queue depth is 2 (with a range of 1-32) and the default read/write timeout value is 60. If the ODM update is not installed, a system administrator will be required to run a chdev (change device) command for every device on the system to change the default attributes.
For details about AIX® ODM for storage, see Hitachi Vantara Support Connect: https://knowledge.hitachivantara.com/Support_Information/Data_Collection/Servers/AIX_ODM_Updates
Cautions
Since the ODM update changes attributes, you might experience problems if you share ports on the storage system with multiple AIX® servers at different ODM update levels (for example, one AIX® host at 5.4.0.0 and one AIX® host at 5.4.0.4). For details about restrictions when sharing ports, contact your Hitachi Vantara representative.