Skip to main content
Delphix

Troubleshooting Storage - Changing Snapshot and/or LogSync Retention (KBA1660)

 

Snapshot policy for both dSources and VDBs are configured either via the Manage > Policies page or on the Configuration > Policies tab for an individual VDB under Manage > Datasets.

The "Default SnapSync" and "Default VDB Snapshot" policies are configured to create snapshots once per day at 3:30 AM local time and the "Default Retention" policy is configured to retain data for 7 days. The amount of storage occupied by an individual snapshot is directly correlated to the amount of unique block changes between the consecutive snapshots.

Storage occupied by individual snapshots can be determined under the Resources > Storage Capacity page, as shown below where the snapshots for a single dSource have been highlighted.

Capacity_snapshots_UI_page.png

If individual snapshots occupy excessive storage space, check whether the retention policy associated with the dSource or VDB can be reduced, provided that such a change would still meet your business requirements.

If the snapshot retention policy for the dSource or VDB cannot be changed, determine whether the retention policy for the transaction logs can instead be reduced.  If it is not necessary to provision or refresh VDBs to a precise point-in-time throughout the entire period covered by the retained snapshots, storage can be freed by only retaining transaction logs for a shorter period.  Doing so would mean that VDBs cannot be provisioned or refreshed to any arbitrary point-in-time beyond the log retention period but they can still provisioned or refreshed to older retained snapshots.  This can help to alleviate storage pressure.

Many users configure their policies to retain snapshots for a longer duration than the transaction logs.  Snapshots are typically far more storage efficient, because a block which is changed 1000 times daily is stored 1000 times in transaction logs but only once in a daily snapshot.  For some users, LogSync is not required at all and disabling it can yield significant storage savings.