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From Katherine Marsden <kmarsdende...@sbcglobal.net>
Subject Re: LOCK_TABLE not cleared (Derby 10.5)
Date Mon, 08 Oct 2012 16:37:33 GMT
On 10/4/2012 3:29 PM, markvarvil wrote:
> Using Derby *10.5*, and running in *network server mode*, we have 
> encountered an issue where the lock_table contained locks, yet these 
> locks are not being deleted; Even after the system sat idle overnight, 
> the locks entries persisted in the lock_table the next morning, and 
> caused the system to function improperly. We are using the default 
> values for lock and deadlock timeouts. Our application is using JPA 
> and Optimistic Locking. What would cause the locks to NOT be cleared 
> and/or released (even after a lengthy timeout period)?

Hi Mark,

Likely there are transactions that have not been committed or rolled 
back that are holding these locks.
The lock timeout  is a setting that will determine how long a new 
transaction will wait for existing  locks to be released before  the new 
transaction times  out  itself. It does not affect how long the original 
transaction will hold the locks which will be until the transaction is 
committed or rolled back.

One thing to do is to make sure that all transactions are committed and 
rolled back, especially in exception
circumstances.  A frequent case I have seen when transactions and 
connections are left open is that transactions are not rolled back 
before attempting to close a connection. Then the exception that is 
thrown on close  is caught and ignored.   A global approach to this 
particular issue might be to replace Connection.close() calls with a 
method that always rolls back before closing the connection.



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