Defining the Storage Groups
- VIO contains data sets less than 20 MB.
- PRIMExx contains data sets greater than, or equal to, 20 MB and less than 285 MB.
- LARGExx contains data sets greater than, or equal to, 285 MB.
The PRIMExx and LARGExx storage groups support temporary data sets that are too large for VIO support. To tailor the storage groups:
- Enter 6 (Storage Group) on the ISMF Primary Option Menu to view the Storage Group Application Selection panel.
- Type in values for the CDS Name, Storage Group Name and Storage
Group Type fields. In this example, the CDS name is YOUR.OWN.SCDS,
the storage group name is VIO, and the storage group type is VIO.
Enter 3 (Alter) to view the VIO Storage Group Alter panel. The VIO Maxsize attribute in the storage group determines the largest temporary data set that can be written to VIO. You determine the size by examining your use of central and expanded storage and your paging activity.
Type in your threshold as the VIO Maxsize attribute if you need to change the 20 MB value. This is the primary space size plus 15 times the secondary space size.
Reasonable limits for VIO depend far more on the sizes of paging data sets than they do on the amount of central storage.
Type in a device type as the VIO UNIT attribute. The VIO device type is virtual and is unrelated to actual devices on your system. Update the Description field to reflect your changes.
Press Enter to verify your changes. Then press PF3 to save the updated storage group. Press PF3 again to return to the Storage Group Application Selection panel.
- Now tailor the PRIMExx storage group.
- Enter a 4 (Volume) on the Storage Group Application Selection panel. Then, specify a volume or range of volumes and enter a 2 (Define) on the Storage Group Volume Selection panel. Define the relationship between the volume and each of your systems or system groups by typing in ENABLE in the SMS VOL STATUS column next to the appropriate system or system group names in the System/Sys Group Name column.
- Optionally, define the LARGExx storage group in the same way as you did for the PRIMExx storage group.
Restriction: If you use VOL=REF processing to refer to a temporary data set, you might get different results in storage group assignments than expected. This is because temporary data sets are assigned a storage group by the system, based on a list of eligible storage groups, such as: VIO, PRIME, STANDARD, etc. Data sets that use VOL=REF are assigned a storage group based on this list of eligible storage groups, not on the name of the storage group used to successfully allocate the first data set being referenced. This might result in the data sets being allocated in different storage groups.