Neoview JDBC Type 4 Driver Programmer's Reference (R2.2, R2.3, R2.4, R2.5)

Statement Pooling
The statement pooling feature allows applications to reuse the PreparedStatement object in
the same way that they can reuse a connection in the connection pooling environment. Statement
pooling is completely transparent to the application.
Guidelines for Statement Pooling
• To enable statement pooling, set the maxStatements property to an integer value greater
than 0 and enable connection pooling. For more information, see “initialPoolSize Property”
(page 41)and “Connection Pooling” (page 27).
• Enabling statement pooling for your JDBC applications might dramatically improve the
performance.
• Explicitly close a prepared statement by using the Statement.close method because
PreparedStatement objects that are not in scope are also not reused unless the application
explicitly closes them.
• To ensure that your application reuses a PreparedStatement, call either of these methods:
— Statement.close method—called by the application
— Connection.close method—called by the application. All the PreparedStatement
objects that were in use are ready to be reused when the connection is reused.
Troubleshooting Statement Pooling
Note the following Type 4 driver implementation details if you are troubleshooting statement
pooling:
• Type 4 driver looks for a matching PreparedStatement object in the statement pool and
reuses the PreparedStatement. The matching criteria include the SQL string, catalog,
current schema, current transaction isolation, and result set holdability. If the Type 4 driver
finds the matching PreparedStatement object, the driver returns the same
PreparedStatement object to the application for reuse and marks the
PreparedStatement object as in use.
• The algorithm, "earlier used are the first to go," is used to make room for caching subsequently
generated PreparedStatement objects when the number of statements reaches the
maxStatements limit.
• The Type 4 driver assumes that any Neoview SQL CONTROL statements in effect at the
time of execution or reuse are the same as those in effect at the time of Neoview SQL
compilation. If this condition is not true, reuse of a PreparedStatement object might
result in unexpected behavior.
• Avoid recompiling to yield performance improvements from statement pooling. The Neoview
SQL executor automatically recompiles queries when certain conditions are met. Some of
these conditions are:
— A run-time version of a table has a different redefinition timestamp than the compile-time
version of the same table.
— An existing open operation on a table was eliminated by a DDL or SQL utility operation.
— The transaction isolation level and access mode at execution time is different from that
at the compile time.
• When a query is recompiled, the Neoview SQL executor stores the recompiled query;
therefore, the query is recompiled only once until any of the previous conditions are met
again.
• The Type 4 driver does not cache Statement object.
28 Accessing Neoview SQL Databases