MDISK - 32-bit CP - V4R4.0
Programming Interface Information:
This information is NOT intended to be
used as Programming Interfaces of z/VM.

MDISK

Prolog  

Control Block Contents  
   MDISK DSECT

Storage Layout  

Cross Reference (Contains links to field and bit definitions)  


MDISK Prolog

 Name       : Minidisk Control Block
 Description: Mini-disk Control Block
 DSECT      : MDISK
 Function   : This control block maps a defined minidisk for
              a virtual machine.
 Located by : VDEVMDSK - Mini-disk block for Reserve/Release
 Created by : HCPVDSLK
 Deleted by : HCPDTDEV, HCPVRILF, HCPVRIRL

 

MDISK Control Block Content


MDISK DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      MDISK          Mini-disk Control Block
     ** FIELDS FOR ATTACH / DETACH
0000    0 Signed       4 MDINEXT        NEXT MDISK ON THIS REAL DEVICE
0004    4 Signed       4 MDILINKS       NUMBER OF LINKS TO THIS EXTENT
     ** FIELDS FOR RELEASE PROCESSING
0008    8 Dbl-Word     8 MDISIOQS (0)   NORMAL START REQUEST QUEUES
0008    8 Signed       4 MDIDEOWD       ANCHOR FOR QUEUE OF UNSOLICITED
                                        IORBKS OWED TO DEVICES
000C   12 Signed       4 MDIDEPND       ANCHOR FOR QUEUE OF PENDING
                                        UNSOLICITED IORBKS
0010   16 Address      4 MDIRTRQ        ADDRESS OF TIMER REQUEST BLOCK
0014   20 Address      4 *              RESERVED FOR FUTURE IBM USE
0018   24 Dbl-Word     8 MDIDIAQS (0)   DIAGNOSE I/O QUEUES
0018   24 Address      4 MDIQWAIT       ANCHOR FOR QUEUE OF IORBKS
                                        WAITING FOR RELEASE TO RETRY
                                        DIAGNOSE I/O
001C   28 Address      4 *              RESERVED FOR FUTURE IBM USE
     ** LOCKS FOR ACCESS TO THE MINIDISK EXTENT
0020   32 Dbl-Word     8 MDILLOCK (0)   LOGICAL LOCK --- DEVICE RESERVED
0020   32 Signed       4 MDIRSVD (0)    VDEVBK HOLDING DEVICE RESERVED
0020   32 Address      4 MDIRVDEV       ADDRESS OF VDEV RESERVING
                                        MINI-DISK (BASE VDEV IF MULTIPLE
                                        EXPOSURE DEVICE)
0024   36 Bitstring    1 MDISTAT        STATUS FLAGS
          1... ....      MDIRESVD       X'80' INDICATES ACTIVE RESERVE
          .1.. ....      MDIRRSVP       X'40' REAL RESERVE IS PENDING
          ..1. ....      MDIRELPD       X'20' REAL RELEASE IS PENDING
          ...1 ....      MDIWRKAL       X'10' Virtual working allegiance
                                        is to be simulated MIDWRKAL
                                        interacts with MDIRESVD and
                                        MDIRVDEV like this : Case I:
                                        MDIRESVD = OFF and MDIWRKAL = ON
                                        Working allegiance is active and
                                        If MDIRVDEV = 0 Then The minidisk
                                        is available. Else MDIRVDEV = the
                                        owning vdev address Case II:
                                        MDIRESVD = ON and MDIWRKAL = OFF
                                        The device is currently reserved
                                        MDIRVDEV = the owning vdev
                                        address MDIRVDEV cannot be zero
                                        Case III: MDIRESVD = ON and
                                        MDIWRKAL = ON The device is
                                        currently reserved MDIRVDEV = the
                                        owning vdev address Working
                                        allegiance may or may not be
                                        active. If the channel program
                                        ended without a Release CCW
                                        issued, then working allegiance
                                        is over but the device is still
                                        unavailable.
0025   37 Bitstring    1 MDILPUM        MASK FOR LOGICAL PATH ON WHICH
                                        RESERVE WAS MADE
0026   38 Bitstring    1 MDIMDCFL       Flag byte for minidisk caching
          1... ....      MDITHUD        X'80' MDC purge on backend is
                                        required
          .1.. ....      MDIOVLAP       X'40' Mini-disk overlapped -
                                        purge cache
          ..11 ....      MDIMDCA        X'30' MDC authorization bits used
                                        only when setting MDIHSHID
          ...1 ....      MDIMDCD        X'10' MDC default authorization
                                        MDC will be prohibited ("SET MDC
                                        MDISK ON" disabled) if: -
                                        minidisk includes CP-system
                                        cylinders. CP's I/O to PAGE,
                                        SPOL, and DRCT space will clash
                                        with any user I/O that is cached.
          .... 1...      MDIMDCP        X'08' MDC prohibited for this
                                        mdisk
          .... .1..      MDIRECAC       X'04' Do record caching for this
                                        mdisk
0027   39 Bitstring    1 MDISMFLG       miscellaneous MDISK flags
          1... ....      MDISMFPO       X'80' The minidisk has a full
                                        pack overlay link to it
          .1.. ....      MDIEXCLU       X'40' Exclusive link held on
                                        minidisk
          ..1. ....      MDIDVFP        X'20' Minidisk created using
                                        DEVNO option
          ...1 ....      MDIQDSK        X'10' Minidisk is a Vdisk
          .... 1...      MDIQDSKP       X'08' Minidisk is a PRIVATE Vdisk
0028   40 Dbl-Word     8 MDILOCK (0)    LOCKWORD FOR RESERVE/RELEASE
                                        STATUS
0028   40 Dbl-Word     8 MDIPLOCK (3)   PHYSICAL LOCK --- EXTENT IN USE
0040   64 Dbl-Word     8 MDIQLOCK (3)   LOCKWORD FOR QUEUE MANIPULATION
     MDISK extent in cylinders (if CKD or ECKD) or blocks (if FBA) These
     values are unique for this real device; no other MDISK block represents
     this exact extent, although other MDISK block extents may overlap this
     extent. Warning: some CKD/ECKD-only routines cannot handle cylinder
     numbers larger than 65535; FBA routines can handle 2**32-1.
0058   88 Dbl-Word     8 MDIVEXTN (0)   Virtual DASD cylinder/block
                                        extents
0058   88 Signed       4 MDIVSEXT       Virtual DASD start cylinder/block
005C   92 Signed       4 MDIVEEXT       Virtual DASD end cylinder/block
     All MDISK blocks representing existing virtual dasds (whether
     "minidisks" or "tdisks" but not "dedicated dasds") are chained in no
     particular order from the RDEV block. The virtual dasd VDEV blocks in
     use on this extent are doubly-chained from this MDISK block in
     descending "link access mode" order. The first VDEV's backward pointer
     points to the end of the chain.
0060   96 Signed       4 MDIVLINK       Pointer to next linked VDEV
     Counts representing the sum of all VDEVs chained from this MDISK having
     the specified "link access mode." See also MDIEXCLU bit in MDISMFPO
     byte. MDILINKS = MDIRDCNT + MDIWRCNT. A stable-read link would be
     counted once in each of MDIRDCNT and MDISTCNT. These counts summarize
     the thousands of VDEVs that could be chained from this MDISK block.
0064  100 Signed       4 MDIRDCNT       Read link count for minidisk
0068  104 Signed       4 MDIWTCNT       Write link count to minidisk
006C  108 Signed       4 MDISTCNT       Stable link count for minidisk
     The minidisk owner is either the user who has the MDISK statement in
     the directory or the user who created this extent (not using the
     directory).
0070  112 Character    8 MDIOUSER       Mini-disk owner userid
0078  120 Signed       2 MDIOVDEV       Mini-disk owner VDEV number
     MDIHSHID may contain one of the following values:
     Zero - This minidisk isn't eligible for MDC caching
     RDEVHSID - when positive, the minidisk is eligible for MDC caching and
     this field is used to create the MDC hash key. When negative (bit 0 is
     on), MDC caching is not permitted for this minidisk.
     X'FFFF' - this minidisk is an FBA device and is not page aligned and is
     not eligible for MDC caching.
     Note that if MDIHSHID is positve, caching is allowed provided that it
     permitted at the system level.
007A  122 Signed       2 MDIHSHID       MDC Hash ID
     MDISK blocks representing tdisks are chained in extent-order from the
     CPVOLume extent EXTBK within which they reside. This mechanism is used
     to distinguish free tdisk space from tdisk space in use.
007C  124 Signed       4 MDITNEXT       Ptr to next MDISK on EXTBK chain
0080  128 Signed       4 MDIEXTBK       Ptr to parent EXTBK
     MDISK blocks representing Vdisks use the following field to chain in
     the Qdisk block.
0084  132 Address      4 MDIQDISK       Address of QDISK block for Vdisk
     Miscellanea
0088  136 Signed       4 MDICYLMP       Minidisk cache cylinder map. If
                                        high order bit on, points to
                                        address of cyl map indicating the
                                        format of each cylinder. If off,
                                        then so far entire mdisk is std
                                        and this field contains the DPSBK
                                        address for that size. Updated
                                        with Compare and Swap.
          00000012       MDISIZE        ((*-MDISK+7)/8) SIZE IN DWS FOR
                                        FREE/FRET

 

MDISK Storage Layout

          
*** MDISK - Mini-disk Control Block
*
*     +---------------------------+---------------------------+
*   0 |         MDINEXT           |         MDILINKS          |
*     +---------------------------+---------------------------+
*   8 |         MDIDEOWD          |         MDIDEPND          |
*     +---------------------------+---------------------------+
*  10 |         MDIRTRQ           |///////////////////////////|
*     +---------------------------+---------------------------+
*  18 |         MDIQWAIT          |///////////////////////////|
*     +---------------------------+------+------+------+------+
*  20 |         MDIRVDEV          |:STAT |:LPUM |:MDCFL|:SMFLG|
*     +---------------------------+------+------+------+------+
*  28 |                                                       |
*     =                       MDIPLOCK                        =
*     |                                                       |
*     +-------------------------------------------------------+
*  40 |                                                       |
*     =                       MDIQLOCK                        =
*     |                                                       |
*     +---------------------------+---------------------------+
*  58 |         MDIVSEXT          |         MDIVEEXT          |
*     +---------------------------+---------------------------+
*  60 |         MDIVLINK          |         MDIRDCNT          |
*     +---------------------------+---------------------------+
*  68 |         MDIWTCNT          |         MDISTCNT          |
*     +---------------------------+---------------------------+
*  70 |                       MDIOUSER                        |
*     +-------------+-------------+---------------------------+
*  78 |  MDIOVDEV   |  MDIHSHID   |         MDITNEXT          |
*     +-------------+-------------+---------------------------+
*  80 |         MDIEXTBK          |         MDIQDISK          |
*     +---------------------------+---------------------------+
*  88 |         MDICYLMP          | 8C
*     +---------------------------+
*
*** MDISK - Mini-disk Control Block

 

MDISK Cross Reference

Symbol         Dspl Value
-------------- ---- -----
MDICYLMP       0088
MDIDEOWD       0008
MDIDEPND       000C
MDIDIAQS       0018
MDIDVFP        0027 20
MDIEXCLU       0027 40
MDIEXTBK       0080
MDIHSHID       007A
MDILINKS       0004
MDILLOCK       0020
MDILOCK        0028
MDILPUM        0025
MDIMDCA        0026 30
MDIMDCD        0026 10
MDIMDCFL       0026
MDIMDCP        0026 08
MDINEXT        0000
MDIOUSER       0070
MDIOVDEV       0078
MDIOVLAP       0026 40
MDIPLOCK       0028
MDIQDISK       0084
MDIQDSK        0027 10
MDIQDSKP       0027 08
MDIQLOCK       0040
MDIQWAIT       0018
MDIRDCNT       0064
MDIRECAC       0026 04
MDIRELPD       0024 20
MDIRESVD       0024 80
MDIRRSVP       0024 40
MDIRSVD        0020
MDIRTRQ        0010
MDIRVDEV       0020
MDISIOQS       0008
MDISIZE        0088 00000012
MDISMFLG       0027
MDISMFPO       0027 80
MDISTAT        0024
MDISTCNT       006C
MDITHUD        0026 80
MDITNEXT       007C
MDIVEEXT       005C
MDIVEXTN       0058
MDIVLINK       0060
MDIVSEXT       0058
MDIWRKAL       0024 10
MDIWTCNT       0068

This information is based on z/VM V4R4.0. Last updated on 29 Jul 2003 at 15:49:52 EDT.
Copyright IBM Corporation, 1990, 2003