Dbvisit log gap report

Dbvisit can report on the difference between the primary and the standby database. This is done with the Dbvisit log gap report. To run the Dbvisit log gap report, run Dbvisit as follows on the primary server:

dbvisit11[/usr/local/dbvisit]> dbvisit -i w120n
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Dbvisit Standby Database Technology
dbvisit started on dbvisit11: Mon May 24 10:08:35 2010
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Contacting Standby Database w120n on dbvisit12...
Last standby sequence obtained (1159) for thread 1.

Dbvisit log gap report for w120n at 201005241008 (thread 1):
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Standby database on dbvisit12 is at sequence: 1159.
Primary database on dbvisit11 is at log sequence: 1160.
Primary database on dbvisit11 is at archived log sequence: 1159.
Dbvisit last transfer log sequence: 1159.
Dbvisit last transfer at: 201005240949.

Archive log gap for w120n:  0.
Transfer log gap for w120n: 0.

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dbvisit ended on dbvisit11
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The report displays the following 2 key values:

  • Archive log gap which is the difference between the last archived sequence on the primary and the last applied sequence on the standby database. The archive log gap should be near 0 (except when APPLY_DELAY_LAG_MINUTES is used).
  • Transfer log gap which is the difference between the last archived sequence on the primary and the last sequence transferred to the standby server. The transfer log gap should be near 0.

The most important value is the Transfer log gap. This value represents your DR exposure. Having this value near 0 means all the available log files have been transferred to the standby server. They may not have been applied to the standby database, but they are queued up and ready to be applied.

The Dbvisit log gap report also:

  • Emails the report to the user specified by the ADMINS email.
  • Inserts the information into the Dbvisit repository to be used for trend analysis reporting purposes.

It is recommended to schedule the Dbvisit gap report every hour. This reporting is non-intrusive. No checkpoints are performed and no logs are transferred.