KnowledgeBase 00101: Configuring QM

This article was originally published as a Tip of the Week.

QM has many configuration parameters. Although the default values may be adequate for development, they are likely to need amending for production use.

The full list of configuration parameters appears in the System Administration section of the QM Reference Manual. This article describes the differences between private and global parameters and reviews ways in which the parameter values can be modified.

Global and Private Parameters

QM has two classes of configuration parameter; global and private. Global parameters set system wide values that can only be changed by restarting the entire QM system. Private parameters take on an initial value specified in the QM configuration file but can be modified on a per-process basis.

The Configuration File

The configuration parameters are defined in a text file named qmconfig in the QMSYS account directory. On Linix systems, the file name is lower case. The data in this file is broken into a number of sections, each starting with a section header that encloses the section name in square brackets. This article considers only the [qm] section.

Each parameter line is of the form

   NAME=value

where NAME is the uppercase parameter name and value is the value to be assigned to this parameter.

Some numeric parameters are defined in the QM Reference Manual as being additive. For example, the FILERULE parameter has three additive values corresponding to different extended file name syntaxes that are to be enabled. The modes with values 1 and 4 could both be enabled with two lines

   FILERULE=1 
   FILERULE=4

or in a single line as

   FILERULE=5

All parameters have default values that will be applied if the parameter is omitted from the qmconfig file. These defaults are shown in the QM Reference Manual.

Viewing Parameter Values

The current values of all configuration parameters can be seen by use of the CONFIG command. Parameters that appear in the qmconfig file and hence may not have their default values are marked with an asterisk. Private configuration parameters that have been modified are marked with a + symbol.

Modifying Parameter Values

Because qmconfig is a simple text file, it can be amended with any convenient text editor. This might be ED or SED from inside QM

   SED $ACC qmconfig

or an operating system editor such as Notepad (Windows) or vi (Linux).

Alteratively, the EDIT.CONFIG command can be used in the QMSYS account. This has the advantage that it performs basic validation of parameter values.

The LICENCE parameter must not be changed manually. New licence details are entered using the UPDATE.LICENCE command.

Whichever method is used, changes to the configuration parameter file do not take effect until QM's shared memory structures are reloaded. On Windows, this requires the QMSvc service to be restarted. On Linux, the qmlnxd dameon must be restarted.

Modifying Private Parameters

A private configuration parameter may be changed within an individual QM process by use of the CONFIG command. For example,

   CONFIG RECCACHE 10

Note that some parameters have special rules about how they are modified. For example, the value of the QMCLIENT parameter that limits what actions can be performed by a QMClient process can be increased but not decreased.

Important Parameters

The most important configuration parameters to consider when installing a new QM system are:

NUMFILES - Sets the upper limit on the number of distinct QM files that can be open simultaneously, system wide. Attempting to open more than this number of files will cause an application to fail.
NUMLOCKS - Sets the maximum number of record locks that can exist system wide at one time. Attempting to lock more than this number of records will cause the process to stall until space is available in the lock table.

None.