MDISK Back to Index page
 
Prolog 
Control Block Contents 
   MDISK DSECT
Storage Layout 
Cross Reference (Contains links to field and bit definitions)
Programming Interface Information:
This information is NOT intended to be
used as Programming Interfaces of z/VM.


  MDISK Prolog Top of page
 
 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
 RELOCATION CONSIDERATIONS : None
 
 
  MDISK Control Block Content Top of page
 

 MDISK DSECT Top of page
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' MDIRESVD INDICATES ACTIVE RESERVE .1.. .... MDIRRSVP X'40' MDIRRSVP REAL RESERVE IS PENDING ..1. .... MDIRELPD X'20' MDIRELPD REAL RELEASE IS PENDING ...1 .... MDIWRKAL X'10' MDIWRKAL 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 Updates serialized by RDEV lock 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 .... ..1. MDIMDTM X'02' MDC disabled by Transport Mode I/O .... ...1 MDIMDCEN X'01' MDC may be enabled for this and/or one or more overlapping mdisk. 0027 39 Bitstring 1 MDISMFLG miscellaneous MDISK flags 1... .... MDISMFPO X'80' MDISMFPO The minidisk has a full pack overlay link to it .1.. .... MDIEXCLU X'40' MDIEXCLU Exclusive link held on minidisk ..1. .... MDIDVFP X'20' MDIDVFP Minidisk created using DEVNO option ...1 .... MDIQDSK X'10' MDIQDSK Minidisk is a Vdisk .... 1... MDIQDSKP X'08' MDIQDSKP Minidisk is a PRIVATE Vdisk .... .1.. MDILOCAL X'04' MDILOCAL Minidisk is local to this system. Set for private minidisks, t-disks, v-disks and minidisks created with DEFINE MDISK. Used by QUERY MDISK DETAILS. .... ..1. MDIPRIVT X'02' MDIPRIVT Minidisk is private to this system on the SUBCONFIG BUILD statement .... ...1 MDIDDEF X'01' MDIDDEF Minidisk created with DEFINE MDISK 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. 008C 140 Signed 4 * Reserved for future IBM use 0090 144 Signed 4 MDIWMASK Mask of system(s) with write link 0094 148 Signed 4 MDILKTOT Count of LINKs issued for this mini 0098 152 Signed 4 MDILKPLX Count of LINK plex consultations 00A0 160 Dbl-Word 8 MDILKTOD Total virtual time for LINKs to consult with the plex 00A8 168 Signed 4 MDIDTTOT Count of DETACHs for this minidisk 00AC 172 Signed 4 MDIDTPLX Count of DETACH plex consultations 00B0 176 Dbl-Word 8 MDIDTTOD Total virtual time for DETACHs to consult with the plex 00B8 184 Signed 4 MDIWKTOT Count of WRKALLEG uses for minidisk 00BC 188 Signed 4 MDIWKPLX Count of WRKALLEG plex consultation 00C0 192 Dbl-Word 8 MDIWKTOD Total virtual time for WRKALLEG uses to consult with the plex 00C8 200 Signed 4 MDIMDOCT Count of times MDC shut off due to write link in plex RESERVED FIELDS FOR INSTALLATION USE THIS AREA IS PERMANENTLY AVAILABLE, BUT MAY BE MOVED TO ANOTHER OFFSET IN THE BLOCK AT A LATER RELEASE OF THE SYSTEM. 00CC 204 Signed 4 MDIUSR1 RESERVED FOR INSTALLATION USE 00D0 208 Signed 4 MDIUSR2 RESERVED FOR INSTALLATION USE 00D4 212 Signed 4 MDIUSR3 RESERVED FOR INSTALLATION USE 00D8 216 Signed 4 MDIUSR4 RESERVED FOR INSTALLATION USE End of Installation reserved fields 0000001C MDISIZE ((*-MDISK+7)/8) SIZE IN DWS FOR FREE/FRET
 
 
  MDISK Storage Layout Top of page
 
          
*** 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          |///////////////////////////|
*     +---------------------------+---------------------------+
*  90 |         MDIWMASK          |         MDILKTOT          |
*     +---------------------------+---------------------------+
*  98 |         MDILKPLX          |///////////////////////////|
*     +---------------------------+---------------------------+
*  A0 |                       MDILKTOD                        |
*     +---------------------------+---------------------------+
*  A8 |         MDIDTTOT          |         MDIDTPLX          |
*     +---------------------------+---------------------------+
*  B0 |                       MDIDTTOD                        |
*     +---------------------------+---------------------------+
*  B8 |         MDIWKTOT          |         MDIWKPLX          |
*     +---------------------------+---------------------------+
*  C0 |                       MDIWKTOD                        |
*     +---------------------------+---------------------------+
*  C8 |         MDIMDOCT          |         MDIUSR1           |
*     +---------------------------+---------------------------+
*  D0 |         MDIUSR2           |         MDIUSR3           |
*     +---------------------------+---------------------------+
*  D8 |         MDIUSR4           | DC
*     +---------------------------+
*
*** MDISK - Mini-disk Control Block
 
 
  MDISK Cross Reference Top of page
 
 
Symbol         Dspl Value
-------------- ---- -----
MDICYLMP       0088
MDIDDEF        0027 01
MDIDEOWD       0008
MDIDEPND       000C
MDIDIAQS       0018
MDIDTPLX       00AC
MDIDTTOD       00B0
MDIDTTOT       00A8
MDIDVFP        0027 20
MDIEXCLU       0027 40
MDIEXTBK       0080
MDIHSHID       007A
MDILINKS       0004
MDILKPLX       0098
MDILKTOD       00A0
MDILKTOT       0094
MDILLOCK       0020
MDILOCAL       0027 04
MDILOCK        0028
MDILPUM        0025
MDIMDCA        0026 30
MDIMDCD        0026 10
MDIMDCEN       0026 01
MDIMDCFL       0026
MDIMDCP        0026 08
MDIMDOCT       00C8
MDIMDTM        0026 02
MDINEXT        0000
MDIOUSER       0070
MDIOVDEV       0078
MDIOVLAP       0026 40
MDIPLOCK       0028
MDIPRIVT       0027 02
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        00D8 0000001C
MDISMFLG       0027
MDISMFPO       0027 80
MDISTAT        0024
MDISTCNT       006C
MDITHUD        0026 80
MDITNEXT       007C
MDIUSR1        00CC
MDIUSR2        00D0
MDIUSR3        00D4
MDIUSR4        00D8
MDIVEEXT       005C
MDIVEXTN       0058
MDIVLINK       0060
MDIVSEXT       0058
MDIWKPLX       00BC
MDIWKTOD       00C0
MDIWKTOT       00B8
MDIWMASK       0090
MDIWRKAL       0024 10
MDIWTCNT       0068
 
This information is based on z/VM 6.3.0 Last updated on 22 May 2013 at 13:54:54 EDT.
Copyright IBM Corporation, 1990, 2013