DYNAMIC_PREPARE Connection Property

• If DYNAMIC_PREPARE is true (the default), every invocation of Connection.prepareStatement during a session attempts to return a precompiled statement in a PreparedStatement object.

  In this case, when a PreparedStatement is executed, the statement it contains is already precompiled in the database, with placeholders for dynamically assigned values, and the statement needs only to be executed.

• If DYNAMIC_PREPARE is false for a connection, the PreparedStatement object returned by Connection.prepareStatement does not contain a precompiled statement.

  In this case, each time a PreparedStatement is executed, the dynamic SQL statement it contains must be sent to the database to be both compiled and executed.

In this example, DYNAMIC_PREPARE is false to disable precompilation of dynamic SQL statements, and props is a Properties object for specifying connection properties.

...
props.put("DYNAMIC_PREPARE", "false")
Connection conn = DriverManager.getConnection(url, props);

When DYNAMIC_PREPARE is true:

• Not all dynamic statements can be precompiled under the prepare command. The SQL-92 standard places some restrictions on the statements that can be used with the prepare command, and individual database vendors may have their own constraints.

• If the database generates an error because it cannot precompile and save a statement sent to it through Connection.prepareStatement, jConnect traps the error and returns a PreparedStatement object containing an uncompiled dynamic SQL statement. Each time the PreparedStatement object is executed, the statement is re-sent to the database to be compiled and executed.

• A precompiled statement resides in memory in the database and persists either to the end of a session or until its PreparedStatement object is explicitly closed. Garbage collection on a PreparedStatement object does not remove the prepared statement from the database.