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Programming Interface Information:
This information is NOT intended to be
used as Programming Interfaces of z/VM. |
MDISK
Control Block Contents
MDISK DSECT
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
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
.... 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
Last updated on 6 Jun 2001 at 11:51:34 EDT.
Copyright IBM Corporation, 1990, 2001