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esources (for example, a DB2 database). After the thread pool limit is reached, the requester
cannot create new physical connections and must wait until a physical connection that is
currently in use is returned to the pool, or a ConnectionWaitTimeout exception is issued.
For example, if you set the Maximum Connections value to 5, and there are five physical
connections in use, the pool manager waits for the amount of time that is specified in
Connection Timeout for a physical connection to become free. The threads waiting for
connections to the underlying resource are blocked until the connections are freed and
allocated to them by the pool manager. If no connection is freed in the specified interval, a
ConnectionWaitTimeout exception is issued.
If you set Maximum Connections property to 0 (zero), the connection pool is allowed to grow
infinitely. This setting has the side effect of causing the Connection Timeout value to be
ignored.
The general guideline for tuning connection factories is that their maximum connection pool
size must match the number of concurrent threads multiplied by the number of simultaneous
connections per thread.
For each JMS, WebSphere MQ, or MQJMS Import, a connection factory exists that was
created during application deployment. Make the Maximum Connections property of the
connection pool, associated with the JMS connection factory, large enough to provide
connections for all threads concurrently running in the import component. For example, if 100
threads are expected to run in a given module, set the Maximum Connections property to 100.
The default is 10.
From the connection factory configuration panel, click Additional Properties Connection
pool properties. Set the Maximum Connections property to the maximum size of the
connection pool.
Configuring data source options
Make the Maximum Connections property of data sources large enough to allow concurrent
access to the databases from all threads. Typically, a number of data sources are configured
in Business Process Manager servers (for example, the BPEDB data source, the TWPROC
data sources, the TWPERFDB data sources, the WPSDB data source, and the messaging
engine database data sources). Set the Maximum Connections property of each data source
to match the maximum concurrency of other system resources as described in 4.7.3, “Tuning
for maximum concurrency” on page 64.
Setting data source prepared statement cache size
The BPC container uses prepared statements extensively. Set the statement cache sizes
large enough to avoid repeatedly preparing statements for accessing the databases.
Set the prepared statement cache for the BPEDB to at least 300.
66 IBM Business Process Manager V8.0 Performance Tuning and Best Practices