JDBC Type 4 Driver Programmer's Reference for SQL/MX Release 3.2.1

7 Module File Caching (MFC)
• “MFC Overview” (page 70)
• “MFC Design” (page 70)
• “Configuring MFC” (page 70)
• “Enabling MFC” (page 70)
• “MFC Usage Scenarios” (page 71)
• “MFC Tuning Recommendations” (page 71)
• “MFC Limitations” (page 72)
MFC Overview
Applications that use the JDBC Type 4 driver might encounter repeated SQL compiles while using
statements and PreparedStatements. To overcome this issue, a driver side Most Frequently
Used (MFU) cache is used. However, the current design of the driver side cache consumes large
amount of memory. The size of the MXOSRVR process memory is directly proportional to the size
of the driver side cache configured through the maxStatements property. Higher
maxStatements value (driver side cache size) can breach the MXOSRVR process memory limit
of 2 GB on the NonStop platform.
The Module File Caching (MFC) feature shares the statement and PreparedStatement plans
among the NonStop SQL/MX database connections. The MFC helps in reducing the SQL compilation
time during JDBC or ODBC application's steady state, thereby reducing resource consumption.
NOTE: Module File Caching is supported only on systems running J06.07 and later J-series RVUs
and H06.18 and later H-series RVUs. Starting with SQL/MX Release 3.2, MFC supports the BigNum
data type in parameterized queries.
MFC Design
For information on the MFC design, see the HP NonStop Connectivity Service Manual for SQL/MX
Release 3.2.1.
Configuring MFC
For information on configuring MFC, see the HP NonStop Connectivity Service Manual for SQL/MX
Release 3.2.1.
Enabling MFC
MFC for the JDBC Type 4 driver is enabled through the MXCS configuration, and SQL modules
are created automatically when statements are prepared. A client program can explicitly turn OFF
MFC if modules are not required.
The following property is required to use MFC in an application that uses the JDBC Type 4 driver:
enableMFC
To enable MFC:
• Change the data source configuration settings on the server side. For more information on
changing the data source settings, see the HP NonStop Connectivity Service Manual.
• The property enableMFC must be set to ON. The default value is ON.
To disable MFC, the value of this property must be set to OFF. For example:
-Dt4sqlmx.enableMFC = OFF.
70 Module File Caching (MFC)