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https://issues.apache.org/jira/browse/DERBY-2921?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12520471
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V.Narayanan commented on DERBY-2921:
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Thank you for looking into this issue and giving your comments Rick. 
Your comments have helped highlight critical issues that would have
risen in the development process.

My proposal to handle the issues pointed out are as follows.

1) Hard-code the SerialVersionUUID. This will help overcome the problem of
   incompatibilities that arise due to difference in the machine that compiles
   the derby release.

2) Place a restriction that all Derby instances in the Relication Closure are 
at the
   same rev level 
   
   For this 

   a) Exchange Derby revision levels during the handshake. If the master and the
      slave are at different rev levels replication will not be allowed.
    
   b) As you suggest update the functional spec to say that Replication fails 
if 
      the master and slave are at different Derby rev levels and it is the 
System 
      Administrator's responsibility to upgrade all Derby installations in 
      the ReplicationClosure at the same time.

   This will handle the issue of incompatible changes made to 
ReplicationMessage and
   also the case where an upgrade is done to the master.

These restrictions will be removed in subsequent revisions.

I will produce an updated functional spec for this.

> Replication: Add a network service that connects the master and slave Derby 
> instances
> -------------------------------------------------------------------------------------
>
>                 Key: DERBY-2921
>                 URL: https://issues.apache.org/jira/browse/DERBY-2921
>             Project: Derby
>          Issue Type: Sub-task
>          Components: Services
>    Affects Versions: 10.4.0.0
>            Reporter: Jørgen Løland
>            Assignee: V.Narayanan
>         Attachments: Replication_Network_v1.diff, Replication_Network_v1.stat
>
>
> A network connection is required between the master and slave Derby instances 
> of a replicated database. The connection will be used to send many kinds of 
> messages, including:
> * log records
> * the database (when replication is started)
> * master -> slave commands (like "stop replication")

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