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.

This page provides an overview of Model 204 parameters and how to use them. For an alphabetical listing of Model 204 parameters, see List of Model 204 parameters.

Basic parameter types

There are seven types of parameters; 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 on this page. The special group parameters (UPDTFILE, PROCFILE, and BLDGFT) are explained in the description of the CREATE command in CREATE command: Permanent group and CREATE command: Temporary group.

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.

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 Structure of CCAIN.

  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.
• 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'}

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.

Short string format

Specify a short string value as a number, as a character string framed by single quotation marks, or as a hexadecimal string framed by single quotation marks.

The format for short string parameters is:

parameter=[-]{number | C'chars' | X'hex'}

Where

• number is a string of decimal digits, 0 to 9.
• chars is any string of characters up to four characters in length.
• hex is a string of hexadecimal digits (0 to 9, A to F) up to eight characters in length.

Short string usually the default

The valid settings for many parameters are supplied with the parameter descriptions later in this section. Some of these descriptions also specify the format for supplying a value; if no format is specified, the parameter accepts short string values. This is the case for most Model 204 parameters.

Summing values

The options for certain parameters can be "summed." For example, the possible settings of CSECHO are:

Setting value	Action
0	Do not echo substitutions to lines.
1	Echo substitutions to lines entered from your input device.td>
4	Echo substitutions to lines input from procedures.td>
5	Echo substitutions to lines from user’s input device and procedures.td>

Entering a value of 5 combines the action of settings 1 and 4.

Validating settings

The valid settings for many parameters are supplied with the parameter descriptions later in this section.

A parameter validation feature checks whether values entered for certain parameters fall within an allowable range. For example, the MVFPG parameter must be in the range 1 to 65535. If a parameter value is outside the range, Model 204 displays messages that the value is either too large or too small and that the value has been incorrectly specified.

Examples of value formats

Examples of specifying parameter values using the RESET command follow.

The following example uses values in decimal format to change the ERMX and PGSEP settings:

RESET ERMX=50,PGSEP=3 ERMX 50 MAXIMUM NUMBER OF ERRORS PGSEP 3 LINES BETWEEN PAGES

The following example uses a value in hexadecimal format to change the setting for LEECHO:

RESET LEECHO=X'05' LEECHO X'05' LINE EDIT ECHO

The following example uses a value in character format to change the setting for ERASE:

RESET ERASE=C'@' ERASE @ X'7C' ERASE CHARACTER SYMBOL

In the following example, the system prompts for parameter specifications after you omit them. You then enter the setting of the CECHO parameter:

RESET *** M204.1119: READING PARAMETERS CECHO=5 CECHO X'05' CARD ECHO

Summary of parameter types

There are several categories of Model 204 parameters. The list below shows the parameter types and how they are designated in the parameter descriptions later in this section:

Type of parameter	Class
System	SYSTEM
Scheduler	CWAIT
User	USER
User table	UTABLE
File characteristics	FPARMS
File table	TABLES
Server	SERVER

The parameter types are summarized below. The list of Model 204 parameters provides links to pages where each parameter is described with its default setting and other characteristics.

System parameters (SYSTEM)

System parameters affect the performance or performance monitoring of Model 204 or provide information about Model 204. Some of these cannot be set, but with the VIEW command they provide important information to the user who examines them.

With the exception of SERVSIZE, you can examine system parameters at any time with the following command:

VIEW SYSTEM

Scheduler parameters (CWAIT)

Scheduler parameters control the Model 204 priority scheduler, which allocates Model 204 resources to individual users based on their relative service requirements.

Examine the parameters in this category with the command:

VIEW CWAIT

User parameters (USER)

User parameters affect the operation of an individual user’s terminal or Model 204 responses during a particular Model 204 session. Using the RESET command, users can change many of these parameters at any time.

Examine these parameters with the command:

VIEW USER

User table parameters (UTABLE)

User table parameters determine how complex a user request can be. You can set most of these parameters on the user’s parameter line and reset them with the UTABLE command.

Examine the UTABLE parameters with the command:

VIEW UTABLE

File characteristics parameters (FPARMS)

File characteristics parameters describe the status and organization of a Model 204 file and the privileges associated with the file.

Examine these parameters with the following command, with a suitable file context specified:

VIEW FPARMS

Only the file manager can set file parameters (some parameters cannot be set). CURFILE and CURLOC are included in the FPARMS category and also in the USER and file table parameters (TABLES).

File table parameters (TABLES)

File table parameters describe the characteristics of the various tables that make up a Model 204 file. Examine the parameters in this category with the command: VIEW TABLES with a suitable file context specified. Only the file manager can set the file table parameters (except for those that cannot be set). CURFILE and CURLOC are included in the TABLES category and also in the USER and file characteristics parameters (FPARMS).

Server parameters (SERVER)

Server parameters are those parameters that are server-specific, for example, SERVSIZE. Unlike the other parameter types, you cannot view server parameters as a category. Server parameters can be set only in the CCAIN stream.

Individual Model 204 parameters

The Model 204 parameter list provides an alphabetical listing of links to individual parameter pages. Each parameter page includes the following information:

• Name of the parameter
• Class or category name (for example, SYSTEM) by which you can examine the parameter with the VIEW command
• Default value of the parameter
• How to set the parameter
• Brief statement of what the parameter means
• Supplementary explanation, when necessary

The defaults are the initial values supplied by Model 204. The system manager can sometimes change these values at initialization, so the defaults for a particular installation might differ from those in the documentation.

The setting line of each parameter description indicates the lowest level of the parameter-setting hierarchy.