DBO - DG Applied Gap alarms firing for Oracle Data Guard databases operating in Snapshot Standby (read-only) mode. (4383999)

Foglight is generating DBO - DG Applied Gap alarms for Oracle Data Guard databases operating in Snapshot Standby (read-only) mode.

Since archive logs are not expected to be applied while the database is in Snapshot Standby mode, is this behavior is expected?

Yes, Snapshot Standby intentionally suspends (or prevents) redo apply while the standby is in snapshot/read-only mode so they can run queries. Because redo is not being applied, any monitor that reports “DG Applied Gap” (i.e., that checks whether archive logs have been applied up to the primary’s sequence) will see a gap and generate alarms.

This is expected behavior from the standpoint of a generic applied-gap check.

WORKAROUND

Option A

• Temporarily silence the specific DBO - DG Applied Gap alarm when you intentionally place the standby into Snapshot mode and re-enable it after conversion back to physical standby.
• Then document an operational playbook to avoid manual validation every time Snapshot Standby is used.

Option B

PSO might be able to help add an alarm condition in the rule to only raise when the standby is in normal physical apply mode.

Basically something along this idea

raise the alarm only if (DATABASE_ROLE = 'PHYSICAL STANDBY') AND (NOT is_snapshot_standby).

The DBO_instance and DBO_Data_Guard_Destination_Status topologies probably can help there.

STATUS

Enhancement ID ISMTS-447 has been logged to suppress alarms for DBO - DG Applied Gap for Oracle Data Guard databases operating in Snapshot Standby (read-only) mode. This will be reviewed by Product Management for consideration in a future release of the Oracle cartridge.