BEA WebLogic Server Tuning Guide

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WebLogic Server will involve the transactional Datasources in its distributed transactions
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. To do this, the underlying
JDBC resource should be XA aware. When a transactional Datasource is configured based on a non-XA aware
driver, WebLogic Server will provide the XA emulation. It is not generally advisable to use this because:
• Only one non-XA aware Datasource (with XA emulation from WebLogic) can participate in a global
transaction.
• The XA-aware driver com.hp.nsk.xares.SQLMXDataSource driver takes precautions to ensure that a proper
transaction context is always available for processing JDBC connections.
When the transactional Datasource is configured with the XA-aware SQL/MX driver (which is a wrapper provided
with WebLogic NonStop Server Toolkit), the Datasource can be used by all EJB and web components that access
multiple resources. The XA resource that is part of the JDBC/MX XA-aware driver depends on the static XA resource
to perform transaction branch coordination between the WebLogic Server TM and TMF. The XA resource in the
driver responds with a READONLY answer to prepare requests, which lets the WebLoic Server TM perform
optimizations with respect to writing logs.
3.6 Disabling the WebLogic Server Prepared Statement Cache
Performance tests have shown that using WebLogic Server Prepared Statement Cache has more overhead in terms
of the path-length on NonStop servers. Disabling the Prepared Statement Cache (the default is that the statement
caching is enabled in WebLogic Server 8.1) provides optimal performance when coupled with JDBC/MX statement
pooling. To disable the WebLogic Server Prepared Statement caching, specify the attribute StatementCacheSize
with a value of 0 in the respective Connection pool configurations.
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As mentioned before, distributed transactions are also called as global transactions. The term distributed here means that branches are contracted to participating
RMs.