Determining dispatchability

By performing an address space analysis on the major system address space, you can determine if there is any work waiting and if the address space is dispatchable. The major address space you should analyze are:

Master scheduler, ASID 1
CONSOLE
JES2/JES3
IMS/CICS/VTAM

When you are analyzing an address space for dispatchability, keep in mind these questions:

Are there any suspended SRBs on the queue?
You will need to run the WEBs on ASCBSAWQ and look for WEBs that have a WEBFLAG1 field of X'000000' to check if there are any SRBs ready to be dispatched.
Are there any ready TCBs indicated by ASCBTCBS and ASCBTCBL?
ASCBTCBS and ASCBTCBL contain a count of the number of TCBs containing ready work to be dispatched. To find the TCBs for ASCBTCBL, look at the WEBs on the ASCBLTCS and ASCBLTCB queues that belong to the home space.
If there is ready work, is the ASCB dispatchable (ASCBDSP1)?
ASCBDSP1 is a non-dispatchability flag. For more information about what the values of ASCBDSP1 indicate, see z/OS® MVS™ Data Areas in z/OS Internet library.
If there is no ready work, are the TCBs in a normal wait (TCBFLGS4, TCBFLGS5, TCBNDSP)?
A non-zero value in any of these fields indicates that the TCB is non-dispatchable.

In Figure 1, ASCBDSP1 is X'04', indicating that this address space is not eligible for CML lock requests. The ASCBSAWQ, ASCBLTCN, and ASCBTCBS fields all contain zeroes, indicating that there is no ready work available.

Figure 1. Example: SUMMARY FORMAT output (determining ready work)

ASCB: 00FD2B80
   +0000  ASCB..... ASCB      FWDP..... 00FC4400  BWDP..... 00000000
   +000C  LTCS..... 00000000  SVRB..... 00F4FBA8  SYNC..... 000727F4
   +0018  IOSP..... 00000000  WQID..... 0000      SAWQ..... 00000000
   +0024  ASID..... 0001      LL5...... 00        HLHI..... 01
   +002A  DPH...... 01FF      LDA...... 7F748EB0  RSMF..... C0
   +0038  CSCB..... 00000000  TSB...... 00000000
   +0040  EJST..... 0000009F  94659288
   +0048  EWST..... AEE06377  45A41803            JSTL..... 000141DE
   +0054  ECB...... 00000000  UBET..... 00000000  TLCH..... 00000000
   +0060  DUMP..... 00699D90  AFFN..... FFFF      RCTF..... 01
   +0067  FLG1..... 00        TMCH..... 00000000  ASXB..... 00FD2EA8
   +0070  SWCT..... 47BE      DSP1..... 00        FLG2..... CE
   +0076  SRBS..... 0000      LLWQ..... 00000000  RCTP..... 00000000
   +0080  LOCK..... 00000000  LSWQ..... 00000000  QECB..... 00000000
   +008C  MECB..... 00000000  OUCB..... 015178E8  OUXB..... 01517BF0
   +0098  FMCT..... 0000      LEVL..... 03        FL2A..... 00
   +009C  XMPQ..... 00000000  IQEA..... 00000000  RTMC..... 00000000
   +00A8  MCC...... 00000000  JBNI..... 00000000  JBNS..... 00FD2B18
   +00B4  SRQ1..... 00        SRQ2..... 00        SRQ3..... 00
   +00B7  SRQ4..... 00        VGTT..... 00CD7458  PCTT..... 1AB6F008
   +00C0  SSRB..... 0000      SMCT..... 00        SRBM..... 07
   +00C4  SWTL..... 00000000  SRBT..... 000015D1  E5E32000
   +00D0  LTCB..... 00000000  LTCN..... 00000000  TCBS..... 00000000
   +00DC  LSQT..... 00000000  WPRB..... 00FD2E90  NDP...... FF
   +00E5  TNDP..... FF        NTSG..... FF        IODP..... FF
   +00E8  LOCI..... 00000000  CMLW..... 00000000  CMLC..... 00000000
   +00F4  SSO1..... 000000    SSO4..... 00        ASTE..... 02900040
   +00FC  LTOV..... 7FFD8400  ATOV..... 7FFDCCA8  ETC...... 0007
   +0106  ETCN..... 0000      LXR...... 0007      AXR...... 0000
   +010C  STKH..... 00FD35C0  GQEL..... 00000000  LQEL..... 00000000
   +0118  GSYN..... 00000000  XTCB..... 006A3D90  CS1...... 00
   +0121  CS2...... 00        GXL...... 02449430
   +0128  EATT..... 0000000E  DAC0D475
   +0130  INTS..... AED8EC7B  0C7C0900            LL1...... 00
   +0139  LL2...... 00        LL3...... 00        LL4...... 00
   +013C  RCMS..... 00000000  IOSC..... 0000450A  PKML..... 0000
   +0146  XCNT..... 01F4      NSQA..... 00000000  ASM...... 00FD3520
   +0150  ASSB..... 00FD2D00  TCME..... 00000000  GQIR..... 00000000
   +0168  CREQ..... 00000000  RSME..... 02219120  AVM1..... 00
   +0171  AVM2..... 00        AGEN..... 0000      ARC...... 00000000
   +0178  RSMA..... 02219000  DCTI..... 0066E2EE

For the mapping structure of WEBs under the IHAWEB, see z/OS MVS Data Areas in z/OS Internet library.

If your address space analysis indicated that ready work was available to be dispatched, look at ASCBDSP1 to determine if the address space is dispatchable. If your address space analysis indicated that there was no ready work available to be dispatched, look at the TCBs to determine if they are in a normal wait. In Figure 2, for example, the TCB fields indicate that the top RB is in a wait.

Figure 2. Example: SUMMARY FORMAT output (determining TCB in normal wait)

TCB: 00FD3608
   +0000  RBP...... 006FF048  PIE...... 00000000  DEB...... 00000000
   +000C  TIO...... 00000000  CMP...... 00000000  TRN...... 00000000
   +0018  MSS...... 7F7463A0  PKF...... 00        FLGS..... 00008004  00
   +0022  LMP...... FF        DSP...... FF        LLS...... 006FFD38
   +0028  JLB...... 00000000  JPQ...... 006FF200
 GENERAL PURPOSE REGISTER VALUES
     0-3  00000001  000027C4  00009FBC  00000004
     4-7  006FFF48  006FEFB8  00F6E900  0000005C
     8-11 80001E52  00C0DCE8  006F5FF0  00FCF778
    12-15 00FCF170  006FF348  80FCF1C0  806FF048
   +0070  FSA...... 00000000  TCB...... 006FF6F0  TME...... 00000000
   +007C  JSTCB.... 00FD3608  NTC...... 00000000  OTC...... 00000000
   +0088  LTC...... 006FF6F0  IQE...... 00000000  ECB...... 00000000
   +0094  TSFLG.... 00        STPCT.... 00        TSLP..... 00
   +0097  TSDP..... 00        RD....... 7F748F04  AE....... 7F746280
   +00A0  STAB..... 00F0B860  TCT...... 00000000  USER..... 00000000
   +00AC  NDSP..... 00000000  MDIDS.... 00000000  JSCB..... 00C0BE84
        .
        .
        .
   +014C  BDT...... 00000000  NDAXP.... 00000000  SENV..... 00000000
   Task non-dispatchability flags from TCBFLGS4:
    Top RB is in a wait