Overview of Model 204 parameters

Parameters are program variables that control or describe Model 204. You can set these variables to different values to tailor system performance to the requirements of an installation or user.

Basic parameter types

There are seven types of parameters (see this summary for more information); the three basic types of parameters are:

• System: Controls the operation of Model 204 as a whole and affects all Model 204 users. Normally the system manager sets these parameters during system installation.
• File: Affects the organization or structure of Model 204 files. Normally the file manager sets these parameters when a file is created.
• User: Affects the operation of a particular user’s terminal or the characteristics of system responses towards that user. The system manager sets some user parameters when initializing Model 204. Other parameters, especially those that control displays, can be set by any user.

Group definition parameters, which cannot be specified with these commands, are not included in this chapter. The special group parameters (UPDTFILE, PROCFILE, and BLDGFT) are explained in the description of the CREATE command.

Viewing parameters

You can examine the current settings of one or more parameters at any time during a Model 204 session. As shown in the example below, the VIEW command can display the values of specific parameters or sets of parameters:

VIEW ERMX, PGSEP ERMX 30 MAXIMUM NUMBER OF ERRORS PGSEP 2 LINES BETWEEN PAGES

The DISPLAY command displays sets of file-related parameters. You can change many parameter values with the RESET or UTABLE command. See Assigning values dynamically: resetting.

How and where to set parameters

Parameters can be assigned new values in a variety of ways. This section describes the initial assignment of parameter values at the beginning of a Model 204 session and dynamic reassignment, or resetting, of values later in the session.

This section does not discuss the requirements for the values assigned to the parameters. These requirements are explained in Requirements for parameter values.

Each Model 204 parameter has a default value supplied by the system. While a value might be appropriate for most installations, system managers have the option to change some defaults to more suitable values.

Some parameters cannot be set; these are view-only parameters that provide information about Model 204.

Assigning initial values

Where parameters are initially set depends on the type of parameter and the operating environment. The different methods of initially setting parameters are listed below.

System parameters

System parameters are initially set with the parameters passed by the operating system when Model 204 is invoked:

• Under IBM z/OS, the parameter names and values must be enclosed in single quotes, as shown in the following example:

  // EXEC PGM=BATCH204,TIME=5,REGION=200K, // PARM='SYSOPT=16'

• Under IBM z/VM, parameters are passed as options of the M204XFER or M204CMS command. For example:

  M204CMS M204ONLN (SYSOPT 152 ALTIODEV 47

• Under IBM z/VSE, the SYSOPT parameter is passed in the UPSI statement. For example, SYSOPT=152 is specified by:

  // UPSI 10011000

  Also under z/VSE, parameters other than SYSOPT (up to a total of eight characters) can be passed in the SYSPARM field. For example:

  OPTION SYSPARM='LIB=512'

• With Host Language Interface IFAM1 runs, you must specify initial parameters in the third argument to the call to the IFSTRT function.
• With Host Language single-threaded IFDIAL runs (using BATCH204), you must specify initial parameters in the third argument of the call to the IFSETUP function. For more details, refer to the Rocket Model 204 Host Language Interface Manual.

User parameters

User parameters are initially set on the User 0 parameter line during system initialization or on any user’s parameter line. Model 204 accepts comment lines or blank lines after the User 0 parameters in the CCAIN input stream.

• The User 0 parameter line is the first line of the CCAIN input data set (after any DEFINE commands) in a batch or online system. This parameter assignment operation is described in detail in the Rocket Model 204 System Manager’s Guide. For example:

  PAGESZ=6184, NFILES=1 . . . EOJ

  With Host Language single-threaded IFDIAL runs (using BATCH204), you can specify User 0 parameters in the fourth argument of the call to the IFSETUP function. For more details, refer to the Rocket Model 204 Host Language Interface Manual.
• Some user parameters are initially set on an individual user’s parameter line. For example:

  IODEV=7,POLLNO=1,NOTERM=1 ERMX=100

File parameters

File parameters are initially set on a parameter line during the CREATE command. For example:

CREATE FILE PEOPLE PARAMETER MVFGP=10,ATRPG=1 END

Assigning values dynamically: resetting

The preceding parameter assignment methods assign initial values to parameters. You can also assign values to many parameters at any time during a Model 204 session. You can set these parameters dynamically with the RESET or the UTABLE command.

Using RESET Change a parameter value with RESET as follows:

RESET ERMX=50

Although any user can issue a RESET command, the settings of certain types of parameters can be modified only by certain types of users. And some parameters cannot be modified at all. If you attempt to change the value of a parameter that cannot be modified, the RESET command is rejected.

Using UTABLE The UTABLE command allows you to change the size of the server tables by modifying the user table parameters. For example:

UTABLE LQTBL=2000

Parameter-setting hierarchy

There is a hierarchy for setting parameters. If a parameter can be reset at command level by any user, then it also can be set as follows:

1. With the parameters passed by the operating system when Model 204 is invoked
2. On the User 0 parameter line
3. On an individual user’s parameter line
4. By the system manager

This hierarchy conforms closely to appearance order in a Model 204 session. Position 1) above, the operating system parameters, appear earliest in the Model 204 startup program; 2) the User 0 parameter line appears after the operating system parameters; 3) an individual user’s parameter line (IODEV line) appears next, the User 0 parameter line; and so on. As long as the permission exists for a given parameter, it can be set or overridden later in the program or session at a position lower in the hierarchy.

Requirements for parameter values

This section’s discussion of requirements for the specification of the values for a parameter describes the permissible value formats, how certain parameter values are summed, and how the valid range of values for a parameter is determined. At the section’s end are examples of parameter formats.

You can specify parameter values in character string format or in short string format.

Character string format

Specify a character string value as a character string framed by single quotation marks.

The format for character string parameters is:

parameter={word | C'chars/var>'}

Where:

• word is any string of characters except a blank space, a comma, an end-of-line character, or an equal sign.
• chars is any string of characters.