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From Pavel Bortnovskiy <pbortnovs...@jefferies.com>
Subject Derby Locks - best practices
Date Fri, 01 Jun 2012 19:16:12 GMT
Hello, all:

Derby is used in my application in the in-memory only mode. For a long time Derby's lock logic
caused no worries, but recently some use cases failed with lock timeouts. Thus I'm looking
for guidance on best practices for handling locks in Derby. A use-case which may cause timeouts
to obtain a lock: one thread is executing an SQL statement which accesses two (or more) in-memory
tables. Those two tables are being modified by  other threads at random times. So, situations
in which the SQL is executed for a long time and the other threads are frequently updating
the tables may cause lock timeouts.

Besides best practices to avoid timeouts and deadlocks, I would like to ask the following
questions:

1)      What's the default length of lock timeouts?

2)      Does my app need another layer of synchronization mechanism/locks to avoid attempts
to update in-memory tables or execute SQLs against them?

3)      Can my application utilize Derby's locks through some API - to query their state or
to use them in making a decision of whether to batch updates or to execute them, to wait or
execute the SQLs?

Your help would be greatly appreciated,

Pavel.
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