SET DISPATCHER

Description

Use the SET DISPATCHER command to change the values of some of the options that CICS dispatcher domain uses for task and TCB management.

These values are set initially by system initialization parameters, described in System initialization parameter descriptions and summary. System initialization parameters that correspond to those in this command have the same or similar names. INQUIRE SYSTEM lists the exact correspondence.

Options

MAXOPENTCBS(data-value)

Specifies, as a fullword binary value, the maximum number of L8 and L9 mode open TCBs that can exist concurrently in the CICS region. The value specified can be in the range of 1 - 4032.

If you reduce MAXOPENTCBS from its previously defined value, and the new value is less than the number of open TCBs currently allocated, CICS detaches TCBs to achieve the new limit only when they are freed by user tasks. Transactions are not abended to allow TCBs to be detached to achieve the new limit. If tasks are queued waiting for an L8 or L9 mode TCB, and you increase MAXOPENTCBS from its previously defined value, CICS attaches a new TCB to resume each queued task, up to the new limit.

For more information about open TCBs see Open TCB management.

Important: By default, CICS uses the MAXTASKS parameter to automatically assign a value to MAXOPENTCBS. Before you explicitly assign a value to MAXOPENTCBS, review the information in Setting the maximum task specification (MXT).

MAXSSLTCBS(data-value)

Specifies, as a fullword binary value, the maximum number of S8 mode open TCBs that can exist concurrently in the CICS region. The value specified can be in the range of 1 - 1024.

For more information about open TCBs see Open TCB management.

MAXXPTCBS(data-value)

Specifies, as a fullword binary value, the maximum number of X8 and X9 mode open TCBs that can exist concurrently in the CICS region. The value specified can be in the range of 1 - 2000.

If you reduce MAXXPTCBS from its previously defined value, and the new value is less than the number of open TCBs currently allocated, CICS detaches TCBs to achieve the new limit only when they are freed by user tasks. Transactions are not abended to allow TCBs to be detached to achieve the new limit. If tasks are queued waiting for an X8 or X9 mode TCB, and you increase MAXXPTCBS from its previously defined value, CICS attaches a new TCB to resume each queued task, up to the new limit.

For more information about open TCBs see Open TCB management.

Important: By default, CICS uses the MAXTASKS parameter to automatically assign a value to MAXXPTCBS. Before you explicitly assign a value to MAXXPTCBS, review the information in Setting the maximum task specification (MXT).

MROBATCH(data-value)

Specifies, as a fullword binary value, the number of events that must occur, from a list of MRO and DASD I/O events on which CICS is waiting, before CICS is posted explicitly to process them. The value must be in the range 1 - 255.

PRTYAGING(data-value)

Specifies, as a fullword binary value, the rate at which CICS is to increase the priority of a task waiting for dispatch. CICS increases the task priority by 1 after each PRTYAGING milliseconds of wait time without a dispatch. The value must be in the range 0 - 65535.

RUNAWAY(data-value)

Specifies, as a fullword binary value, the default for runaway task time. This global value for the CICS region is used for any task running a transaction that does not specify an explicit runaway task time.

The value must be either zero, which means that runaway task detection is not required for tasks using the default value, or in the range 500 - 2 700 000. The value you supply is rounded down to the nearest multiple of 500.

SCANDELAY(data-value)

Specifies, as a fullword binary value, the terminal scan delay value for the CICS region in milliseconds, which is initially set by the ICVTSD system initialization parameter. The default setting is zero. The value must be in the range 0 - 5000. The terminal scan delay facility was used in earlier releases to limit how quickly CICS dealt with some types of terminal output requests made by applications, in order to spread the overhead for dealing with the requests. Specifying a nonzero value was sometimes appropriate where the CICS system used non-SNA networks. However, with SNA and IPIC networks, setting ICVTSD to 0 is appropriate to provide a better response time and best virtual storage usage.

TIME(data-value)

Specifies, as a fullword binary value, the maximum interval in milliseconds for which CICS gives control to the operating system if no tasks are ready for dispatch. This value is set initially by the ICV system initialization parameter and is sometimes called the region exit time interval. The TIME value must be in the range 100 - 3 600 000 and must not be less than the SCANDELAY value. You can determine the current SCANDELAY value, if you are not setting it at the same time, with the INQUIRE DISPATCHER SCANDELAY command.

Conditions

INVREQ

RESP2 values:

5

The TIME value is not in the range 100 - 3 600 000.

6

The RUNAWAY value is out of range.

7

MROBATCH is not in the range 1 - 255.

13

TIME is less than SCANDELAY.

14

PRTYAGING is not in the range 0 - 65535.

15

SCANDELAY is not in the range 0 - 5000.

26

The MAXOPENTCBS value is less than the TCBLIMIT on the DB2CONN resource definition when CICS is connected to DB2®.

27

The MAXOPENTCBS value is out of range.

30

The MAXSSLTCBS value is out of range.

31

The MAXXPTCBS value is out of range.

NOTAUTH

RESP2 values:

100

The user associated with the issuing task is not authorized to use this command.