MX Release 3.2.1 (H06.26+, J06.15+)

For information on the ODBC/MX driver support for MFC, see the HP NonStop ODBC/MX Driver

for Windows for SQL/MX Release 3.2.1.

Design of MFC

MFC shares static module files created from dynamic queries using SQL/MX tools, across MXOSRVR

or SQL/MX connections.

MFC uses disk files on the NonStop Open System Services file system for storing the compiled

SQL/MX prepared statement plans. When the application uses prepareexecute or execdirect API,

MFC checks for an existing plan that matches the query. If a plan exists, it is loaded from the disk

thereby eliminating the requirement of SQL compilation of the query.

If a plan for an incoming PREPARE statement for a query is not found on the disk, a plan is created

as follows:

1. The incoming query is compiled as any other SQL/MX prepared statement.

2. After successful completion of the SQL/MX prepared statement, a plan is generated and stored

in the directory specified in the compiled_module_location attribute of SQL/MX.

Synchronization issues are handled using temporary lock files.

Use an MFC management script for maintaining the compiled module plans on the NonStop server.

The MFC management script is described under “Managing MFC” (page 51).

In releases prior to SQL/MX Release 3.2.1, the MXOSRVR waits until the SQL query compilation

generates the MFC file, thus blocking the client. Starting with SQL/MX Release 3.2.1, this limitation

is overcome by running the MFC file generation process in the background. As a result of this

optimization, MFC module files may fail to generate for few SQL queries if any DDL query such

as DROP or ALTER is executed immediately after compilation of the SQL query.

Configuring MFC from the MXCS mode

To configure the module file caching feature using the MXCS subsystem:

1. Enter the MXCS subsystem through MXCI:

mode mxcs;

2. Configure a data source for the user-specified MXOAS service:

add ds $MXOAS.”MCBS_datasource”;

NOTE: For instructions on adding a data source, see the SQL/MX Connectivity Service

Administrative Command Reference manual.

3. Stop the data source:

stop ds “MCBS_datasource”, reason ‘test’;

NOTE: Perform step 3 only if the configured data source is in the started state.

4. Add the statement_module_caching attribute to the data source to enable the module

file caching feature:

add evar $MXOAS.”MCBS_datasource”.statement_module_caching, type

set, value ‘true’;

This attribute has only two values, true and false. By default, this attribute is not enabled.

5. Add the compiled_module_location attribute to the data source:

add evar $MXOAS.”MCBS_datasource”.compiled_module_location, type

set, value ‘default’;

add evar $MXOAS.”MCBS_datasource”.compiled_module_location, type

set, value ‘/usr/MCBS_modules’;

Module File Caching (MFC) 49