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From Øystein Grøvlen (JIRA) <j...@apache.org>
Subject [jira] Commented: (DERBY-2872) Add Replication functionality to Derby
Date Tue, 24 Jul 2007 09:00:36 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12514921

Øystein Grøvlen commented on DERBY-2872:

V.Narayanan (JIRA) wrote:
>> If you use the non-blocking backup mechanism, you will have to copy
>> both database and log files and you will probably want to delay
>> switching to replication of individual log records until the backup
>> is completed.
> Switching between two different messages sent across the network seems
> like additional complication which we can avoid if we do not use online
> backup. But then there is the additional complexity of handling unlogged
> operation which online backup has already solved.

My thouhgt was that you could use the same mechanism to send both data files and log files
from the backup. 

> Would the requirement of 2x space qualify not using online backup?

I do not think so. 

> I the comments above a case has been pointed out
> "If an transaction has been open since before replication was started, a
> slave may need log from before log shipping started to be able to undo
> the transaction at failover time."
> Would it be easy in this case too? How would the switching happen in this
> case?

The switch will be the point where you switch from sending log files to sending individual
log records.  The issue about old transaction only affects how old log files you need to send,
not when to switch.

> Add Replication functionality to Derby
> --------------------------------------
>                 Key: DERBY-2872
>                 URL: https://issues.apache.org/jira/browse/DERBY-2872
>             Project: Derby
>          Issue Type: New Feature
>          Components: Miscellaneous
>    Affects Versions:
>            Reporter: Jørgen Løland
>            Assignee: Jørgen Løland
>         Attachments: proof_of_concept_master.diff, proof_of_concept_master.stat, proof_of_concept_slave.diff,
proof_of_concept_slave.stat, replication_funcspec.html, replication_funcspec_v2.html, replication_funcspec_v3.html,
> It would be nice to have replication functionality to Derby; many potential Derby users
seem to want this. The attached functional specification lists some initial thoughts for how
this feature may work.
> Dag Wanvik had a look at this functionality some months ago. He wrote a proof of concept
patch that enables replication by copying (using file system copy) and redoing the existing
Derby transaction log to the slave (unfortunately, I can not find the mail thread now).
> DERBY-2852 contains a patch that enables replication by sending dedicated logical log
records to the slave through a network connection and redoing these.
> Replication has been requested and discussed previously in multiple threads, including
> http://mail-archives.apache.org/mod_mbox/db-derby-user/200504.mbox/%3c426E04C1.1070904@yahoo.de%3e
> http://www.nabble.com/Does-Derby-support-Transaction-Logging---t2626667.html

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