DCMT DISPLAY SUBTASK Command

DCMT DISPLAY SUBTASK allows you to display information about operating system subtasks.
idmscu19
DCMT DISPLAY SUBTASK allows you to display information about operating system subtasks.
This article describes the following information:
2
2
Syntax
►►─── DCMT ─┬───────────────────┬─────────────────────────────────────────────►             └─ 
broadcast-parms
 ─┘  ►─── Display ─┬─ SUBTask EFFectiveness ──┬───────────────────────────────────►◄                ├─ SUBTask 
subtask-number
 ─┤                └─ SUBTasks ───────────────┘
Parameters
  • broadcast-parms
    Indicates to execute the DCMT command on all or a list of data sharing group members.
    For more information about broadcasting and
    broadcast-parms
    syntax, see How to Broadcast System Tasks the section.
  • SUBTask EFFectiveness
    Displays CPU effectiveness
  • SUBTask
    Displays detailed information about the specified operating system subtask.
    • subtask-number
      The ID of a subtask.
  • SUBTasks
    Displays summary information about all subtasks.
Usage
DCMT DISPLAY SUBTASK
Displays the following information for the specified subtask or for each subtask:
Field
Value
Name
The name of each subtask
Number
The number of each subtask
Status
The current status of the subtask (IDLE or BUSY)
Work type
One of the following types of work the subtask can execute:
I or IDMS -- Database and communication work
U or UTIL -- Utility subtask work
Count wakeups
The number of times DC/UCF restarted this subtask.
Count task dispatches
The number of times DC/UCF dispatched this subtask.
User mode CPU time
The amount of time this subtask spent in user-mode execution.
System mode CPU time
The amount of time this subtask spent in system-mode execution.
CPU effectiveness (%)
The percentage comparison of CPU time to wall clock time while the subtask was executing. A subtask is considered to be executing if it has not been put into a WAIT state by the CA IDMS system. An executing subtask can lose effective CPU time due to paging or to other tasks being given a higher priority by the operating system.
Count times fast posted
The number of times the IDMS postexit was able to post an ECB without requiring a call to the operating system while running on this subtask.
Count times 0S posted
The number of times the operating system's post SVC was used to post an ECB. This field should always be zero unless operating sytem PC routines are not available.
Count found work pass 1
The number of times the IDMS dispatcher found work queued to the global dispatch work queue (CSAWKQUE) while using this subtask.
Count found work pass 2
The number of times the IDMS dispatcher found work to dispatch while scanning the DCE active chain using this subtask.
Count times POSTEXIT resumed
The number of times the operating system woke the IDMS system up through its PCRESUME routine using this subtask.
DCMT DISPLAY SUBTASK 000n
(z/OS systems only) Displays the following CPU statistics under Enclave Info when zIIP support is active:
Field
Value
zIIP time
The CPU time consumed while physically executing on a zIIP processor.
zIIP on CP time
The system mode CPU time consumed on a CP because zIIP is unavailable.
CPU effectiveness
The percentage comparison of CPU time to wall-clock time while the subtask was executing. A subtask is considered to be executing if it has not been put into a WAIT state by the CA IDMS system. An executing subtask can lose effective CPU time due to paging or to other tasks being given a higher priority by the operating system. Reported CPU effectiveness can exceed 100% due to pro-rating techniques used by the operating system to compensate for relative speed differences between the CP and zIIP.
DCMT DISPLAY SUBTASK EFFECTIVENESS
Displays whether zIIP support is active by subtask and displays the following fields for each TCB and SRB:
Field
Value
Name
The name of each subtask.
Elapsed time
The length of time the subtask or SRB has been running.
Total CPU time
The amount of CPU time the subtask or SRB has used.
CPU effectiveness
The percentage comparison of CPU time to wall-clock time while the subtask was executing. A subtask is considered to be executing if it has not been put into a WAIT state by the CA IDMS system. An executing subtask can lose effective CPU time due to paging or to other tasks being given a higher priority by the operating system. Reported CPU effectiveness can exceed 100% due to pro-rating techniques used by the operating system to compensate for relative speed differences between the CP and zIIP.
Subtask Naming Convention
The first subtask that DC/UCF allocates is named MAINTASK. Subsequently allocated subtasks are used only with multitasking or when utility subtask support is activated. They have names that are configured as follows:
SUBT
nnnn
The first subtask that is allocated after MAINTASK is SUBT0001, the second SUBT0002, and so forth.
Subtask Numbering Conventions
When DC/UCF allocates subtasks for a given it gives each subtask a number. MAINTASK is always subtask 1 (0001), the next subtask that is allocated is number 2, and so forth.
The 
total
 number of subtasks on the system is determined at system startup time, in the startup JCL.
When DC/UCF Restarts Subtasks
To reduce overhead, DC/UCF only restarts (wakes up) an operating system subtask when DC/UCF tasks are queued for the next associated system service. When this happens, DC/UCF assigns the 
next
 task that requests the queued service to an idle subtask.
Examples
DCMT DISPLAY SUBTASKS
      D SUBT                                                                            ***  Display all subtasks ***                                                            Work            Task dispatch                                     Name       Nr  type  Status         count        Wakeup count   Total CPU time   ----       --  ----  ------    -------------     ------------   --------------   MAINTASK   01  IDMS   IDLE             3,952            3,814    00:00.953886    SUBT0001   02  IDMS   IDLE                00               00    00:00.000032    SUBT0002   03  IDMS   IDLE                00               00    00:00.000021    SUBT0003   04  IDMS   IDLE                00               01    00:00.000045    SUBT0004   05  IDMS   IDLE               132               10    00:00.006961    SUBT0005   06  IDMS   IDLE               895               93    00:00.024675    SUBT0006   07  IDMS   BUSY            20,916            9,585    00:01.934314   V214  ENTER NEXT TASK CODE:      CA IDMS release nn.n tape GJI00B node SYSQA14  
zIIP-Enabled Examples with a zIIP Processor
The following series of examples illustrate a CA IDMS system running in multitasking mode with zIIP support enabled. The displays were obtained on hardware that contained five CPs and one zIIP.
DCMT DISPLAY SUBTASK 0001
 *** Display Subtask details ***                                                                         Name  MAINTASK                                                               Number  01                                                                     Status  IDLE                                                                Work type  IDMS                                                            Count wakeups  3,814                                                   Count task dispatches  3,952                                                      User mode CPU time  00:00:00.000955                                          System mode CPU time  00:00:00.953883                                         CPU effectiveness (%)  09                                                    Count times fast posted  15                                                      Count times OS posted  00                                                    Count found work pass 1  3,869                                                 Count found work pass 2  83                                               Count times POSTEXIT resumed  3,814                                                                 *** Enclave Info ***                                                         zIIP time  00:00:00.099662                                               zIIP on CP time  00:00:00.000000                                         CPU effectiveness (%)  75                                                        Count swap attempts  8,072                                                      Count actual swaps  8,065                                         
DCMT DISPLAY SUBTASK 0006
The following example illustrates the additional information that is provided for the preferred subtask:
      D SUBT 0006                                                               *** Display Subtask details ***                                                                         Name  SUBT0005                                                               Number  06                                                                    Status  IDLE                                                                Work type  IDMS                                                            Count wakeups  83                                                      Count task dispatches  1,667                                                      User mode CPU time  00:00:00.002093                                          System mode CPU time  00:00:00.037788                                         CPU effectiveness (%)  11                                                    Count times fast posted  02                                                      Count times OS posted  00                                                    Count found work pass 1  1,376                                                 Count found work pass 2  291                                              Count times POSTEXIT resumed  83                                                                    *** Enclave Info ***                                                         zIIP time  00:00:00.011148                                               zIIP on CP time  00:00:00.000000                                         CPU effectiveness (%)  13                                                        Count swap attempts  1,767                                                      Count actual swaps  1,761                                         
DISPLAY SUBTASK EFFECTIVENESS
The following example illustrates whether zIIP support is active by subtask. It includes CPU statistics for each subtask and associated SRB, and percentage comparison of CPU effectiveness.
      D SUBT EFF                                                                 *** Subtask display ***                                                         Subtask          Elapsed time                  Total CPU time         % CPU  SRB  Name         TCB            SRB            TCB            SRB       TCB SRB     -------- -------------- -------------- -------------- -------------- --- ---     MAINTASK   00:09.273726   00:00.131952   00:00.854224   00:00.099662  09  75  Y  SUBT0001   00:00.000142   00:00.000015   00:00.000032   00:00.000000  22  00  Y  SUBT0002   00:00.000074   00:00.000011   00:00.000021   00:00.000000  28  00  Y  SUBT0003   00:00.000117   00:00.000029   00:00.000045   00:00.000000  38  00  Y  SUBT0004   00:00.007514   00:00.001178   00:00.006361   00:00.000600  84  50  Y  SUBT0005   00:00.112166   00:00.019377   00:00.017645   00:00.007029  15  36  Y  SUBT0006   00:02.799915   00:02.270030   00:01.109634   00:00.827857  39  36  Y  -------- -------------- -------------- -------------- -------------- --- ---     Totals     00:12.193658   00:02.422595   00:01.987965   00:00.935150  16  38     V214  ENTER NEXT TASK CODE:      CA IDMS release nn.n tape GJI00B node SYSQA14 
zIIP-Enabled Example Without a zIIP Processor
The following example illustrates a CA IDMS system running in multitasking mode with zIIP support enabled. The display was obtained on hardware that contained two CPs and no zIIP.
DCMT DISPLAY SUBTASK 0003
  *** Display Subtask details ***                            Name  SUBT0002                          Number  03                          Status  BUSY                       Work type  IDMS                   Count wakeups  80,836,576           Count task dispatches  96,549,679              User mode CPU time  00:00:00.0251            System mode CPU time  00:17:10.3946           CPU effectiveness (%)  27         Count times fast posted  10,451,388           Count times OS posted  00         Count found work pass 1  96,256,979         Count found work pass 2  292,700    Count times POSTEXIT resumed  80,639,015                         *** Enclave Info ***                       zIIP time  00:00:00.0000                 zIIP on CP time  00:05:39.9737           CPU effectiveness (%)  41             Count swap attempts  60,356              Count actual swaps  60,336
More Information
  • For more information about multitasking support, see the
    System Reference section
    .
  • For more information about enabling and using zIIP support, see the
    System Reference section
    .