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From Kathey Marsden <kmarsdende...@sbcglobal.net>
Subject Re: Backup : snapshot at beginning or mixed content ?
Date Mon, 06 Sep 2010 20:49:45 GMT
  On 9/6/2010 9:32 AM, Maison Mo wrote:
> Hello dear derby developers,
>
> I have a question about database backup.
>
> According to admin guide, there are two methods for that operation :
> 1 - freeze the DB with SYSCS_UTIL.SYSCS_FREEZE_DATABASE and perform a 
> (hopefully quick) external copy of database files ; then UNFREEZE
> 2 - Use SYSCS_UTIL.SYSCS_BACKUP_DATABASE(...)
>
> I wonder what happens when commits are performed during the backup.
> - With method 1 I expect the commits to hang until the unfreeze
> - With method 2 what happens exactly ? Does the commit go into the 
> backup ? Always ? Never ? Does it depends on the table(s) on which the 
> commit is performed ?
>
Assuming you are using a current version, I believe you are safe using 
online-backup which should not block which was introduced in 10.2[1].  
There are a few exceptions regarding  unlogged operations, see online 
backup documentation [2]:

Uncommitted transactions do not appear in the backed-up database and new 
commits that occur during the backup  will not appear in the backup.


Thanks Kathey
[1] https://issues.apache.org/jira/browse/DERBY-239
[2]http://db.apache.org/derby/docs/10.5/adminguide/cadminhubbkup01.html


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