CEMT SET DISPATCHER
Change the system values used by CICS® dispatcher.
In the CICS Explorer, the Regions operations view provides a functional equivalent to this command.
Syntax
Press the Clear key to clear the screen.
You can start this transaction in two ways:
- Type
CEMT SET DISPATCHER(or suitable abbreviations ofr the keywords). The resulting display lists the current status, similar to that obtained by using the CEMT INQUIRE DISPATCHER command. You can tab to the highlighted or blank fields and overtype them with the required values. - Type
CEMT SET DISPATCHER(or suitable abbreviations ofr the keywords), followed by one or more attributes that you want to change.
Typing ? at the beginning of either the
first or second line gives a syntax prompt.
Options
- AGING (value)
- Specifies
the time factor for CICS to
use in the priority aging algorithm to increment the priority of a
task. The value is expressed as
milliseconds per unit of priority
, and must be in the range 00000 - 65535. The priority aging factor is defined initially by the PRTYAGE system initialization parameter, in which the value represents the number of milliseconds that must elapse before the priority of a waiting task can be adjusted upward by 1. See PRTYAGE for information about the PRTYAGE system initialization parameter. - MAXOPENTCBS(value)
- Specifies
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 1 - 4032. If you reduce MAXOPENTCBS
from its previously defined value, and the new value is less than
the number of open TCBs currently allowed, 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 there are
tasks 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(value)
- Specifies the maximum number of S8 mode open TCBs that can exist concurrently in the CICS region. The value specified can be in the range 1 - 1024. For more information about open TCBs, see Open TCB management.
- MAXXPTCBS(value)
- Specifies
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 1 - 2000. If you reduce MAXXPTCBS from
its previously defined value, and the new value is less than the number
of open TCBs currently allowed, 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 there are tasks 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 (value)
- Specifies the number of MRO requests from connected regions that are to be batched before this region is posted. The value is in the range 001 - 255.
- RUNAWAY (value)
- Specifies
the interval, in milliseconds, for which a task can have control before
it is assumed to be looping.
You can specify 0, or a value in the range 500 - 2700000. The value chosen is rounded down to a multiple of 500. CICS purges a task if it has not given up control after this interval (that is, if the task appears to be looping). If you specify zero, runaway task control is inoperative (that is, tasks do not get purged if they appear to be looping). The value is independent of, and can be less than, the value in the TIME operand.
CICS runaway-task detection is based upon task time, that is, the interval is decremented only when the task has control of the processor. You do not, therefore, need to allow for the effect of other jobs when setting the value.
- SCANDELAY (value)
- Specifies the terminal scan delay value for the CICS region, which is initially set by the ICVTSD system initialization parameter. The default value is zero. 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. If required, you can reset this value by overtyping it with a different value in the range 0–5000 milliseconds.
- TIME (value)
- Specifies
the interval, in milliseconds, for which CICS releases control to the operating system
if no transactions are ready to resume processing. This interval is
known as the region exit interval.
It can have a value in the range 100 - 3600000, and must be greater than or equal to the SCANDELAY value.
In the summary report of the dispatcher statistics, TIME is referred to as ICV.