Collocation of retention storage pools

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The value that you select for the collocation property affects how a retention set's data is distributed across tape volumes. In general, to nimize the number of tape volumes, disable collocation. By default, the collocation setting for retention storage pools is disabled.

When you disable the collocation setting, the server attempts to use all available space on each tape volume before it selects a new volume. Although this process makes more efficient use of individual tape volumes, the data for each retention set is not collocated and might be distributed across many tape volumes.

Performance considerations: Your collocation settings can have a significant impact on system performance. System performance might decrease when the retention set data is written to tape and during restore operations. Before you enable collocation settings for retention storage pools, consider your organization's requirements and the performance tradeoffs. If collocation is enabled, the server tries to keep files for each entity on a minimal number of tape volumes. However, this option increases both the server processing time to collocate the files and the number of required tape volumes.
Where the system copies data is also affected by the STACK parameter value that you specify for a retention set:
Yes
The retention set data can share tape volumes with data that is copied from other retention sets. During volume selection, the first volumes to be filled are those that are already in a FILLING state, but only if those volumes are not already in use by retention sets that require a separate volume.
No
The retention set is collocated on one or more tape volumes and data from other retention sets is not placed on those volumes. Empty volumes are filled first, but data can also be copied to FILLING volumes if the volumes already contain data for the retention set that is being copied.
Restrictions:

  • The STACK parameter applies only when you copy retention data to tape volumes. The parameter is ignored when you copy retention data to cloud storage.

  • The collocation setting affects only the data that is written to the retention storage pool after the setting is changed. Files that are already stored in the pool are not affected.

You can enable collocation or change collocation settings by specifying the COLLOCATE parameter on the DEFINE STGPOOL or UPDATE STGPOOL commands.Empty volumes are filled first,