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log gap

Posted on 2014-04-07
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Last Modified: 2014-04-08
What is actually log gap ?


How we will find that  ?
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Question by:tonydba
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Wasim Akram Shaik earned 500 total points
ID: 39983270
--->What is actually log gap ?


Archive gaps are simply a range of archived redo logs that were created at a time when the standby database was not available to receive them as they were being generated by the primary database. These archive gaps occur most often during network unavailability between the primary and standby database. During network outages like this, the standby database fails to receive any redo data from the primary database. When the network failure has been resolved, automatic transmission of redo data from the primary to the standby database is resumed. The missing archived redo logs signify the gap.

--->How we will find that  ?

select * from v$archive_gap;

References from

http://www.idevelopment.info/data/Oracle/DBA_tips/Data_Guard/DG_5.shtml

to Fix archive log gap check this

http://www.dba-oracle.com/t_oracledataguard_156_physical_standby_archive_gap.htm

http://www.dba-oracle.com/t_detect_redo_log_gaps.htm
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Expert Comment

by:slightwv (䄆 Netminder)
ID: 39983848
It doesn't have to necessarily be related to a standby database and dataguard.

If can also just be a missing archived redo log for a normal database.

In a nutshell:
to perform a recovery you need EVERY archived redo log in sequence.  If you are missing one, there is a gap.  You cannot recover a database past the point of the mising archived redo log.
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Author Closing Comment

by:tonydba
ID: 39986493
Yes log gap understood..
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