Why Archive Gets Mounted / Dismounted ?

Yesterday talking in the otn forum, someone asked about messages in the alert.log of the database, it indicatd mount and dismount continuously for a diskgroup. This can be frightening when you first see it, but is normal and usual when there is no activity against the database, or rather are not using the files that are in that diskgroup. This is a excerpt from alert.log;

 

Thu Sep 04 11:15:07 UTC 2014
Thread 1 advanced to log sequence 611 (LGWR switch)
  Current log# 2 seq# 611 mem# 0: +SIEBEL_DG/sibpro/onlinelog/group_2.940.856925893
Thu Sep 04 11:15:07 UTC 2014
SUCCESS: diskgroup SIBP_PROD_ARCSITE_DG was dismounted
Thu Sep 04 11:15:08 UTC 2014
SUCCESS: diskgroup SIBP_PROD_ARCSITE_DG was mounted
Thu Sep 04 11:15:13 UTC 2014
SUCCESS: diskgroup SIBP_PROD_ARCSITE_DG was dismounted
Thu Sep 04 11:23:50 UTC 2014
Thread 1 advanced to log sequence 612 (LGWR switch)
  Current log# 3 seq# 612 mem# 0: +SIEBEL_DG/sibpro/onlinelog/group_3.939.856625793
Thu Sep 04 11:23:50 UTC 2014
SUCCESS: diskgroup SIBP_PROD_ARCSITE_DG was mounted
Thu Sep 04 11:23:56 UTC 2014
SUCCESS: diskgroup SIBP_PROD_ARCSITE_DG was dismounted
Thu Sep 04 11:24:03 UTC 2014

 

This is expected behavior. Although the messages appear in the alert.log not mean they are errors in this case are messages of information.

One trick to prevent these messages from appearing is to put a mirrored online redo or mirrored  Control-a file on the diskgroup. This what this does is it continually open the diskgroup.

 

HTH – Antonio NAVARRO

 

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