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From "Suresh Thalamati (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-239) Need a online backup feature that does not block update operations when online backup is in progress.
Date Fri, 28 Oct 2005 22:05:56 GMT
    [ http://issues.apache.org/jira/browse/DERBY-239?page=comments#action_12356240 ] 

Suresh Thalamati commented on DERBY-239:

What to do if backup is started in a transaction that  already has unlogged operations executed?

In  previous discussions about online backup, it was concluded that existing 
backup procedures calls will WAIT for the transaction with unlogged 
operations to commit before proceeding with the backup. One issue that was
missing from the discussion was, what to do if user starts a backup 
in the same transaction that has unlogged operations executed before the backup call. 
WAIT will  not be an acceptable option here, because backup call will wait forever. 

I can think of two ways this issue can be addressed:

1) Add a restriction that backup procedures can only be called in a brand
   NEW transaction. And also implicitly commit the backup transaction at the end of the 
   backup. Commit is not required as such to solve this problem, but it would
   be cleaner because backup itself is not a rollback-able operation. 
2) Make backup procedures fail, if transaction that it is started in 
   contains unlogged operations.

I am inclined towards implementing the first option. Any comments/suggestion 
will be appreciated. 


> Need a online backup feature  that does not block update operations   when online backup
is in progress.
> --------------------------------------------------------------------------------------------------------
>          Key: DERBY-239
>          URL: http://issues.apache.org/jira/browse/DERBY-239
>      Project: Derby
>         Type: New Feature
>   Components: Store
>     Versions:
>     Reporter: Suresh Thalamati
>     Assignee: Suresh Thalamati
>  Attachments: onlinebackup.html, onlinebackup_1.diff
> Currently Derby allows users to perfoms  online backups using SYSCS_UTIL.SYSCS_BACKUP_DATABASE()
procedure,  but while the backup is in progress, update operations are temporarily blocked,
but read operations can still proceed.
> Blocking update operations can be real issue specifically in client server environments,
because user requests will be blocked for a long time if a 
> backup is in the progress on the server.

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