ALOC Back to Index page
 
Prolog 
Control Block Contents 
   ALOC 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.


  ALOC Prolog Top of page
 
 NAME       : HCPALOC
 DESCRIPTION: DASD VOLUME ALLOCATION BLOCK
 DSECT      : ALOC
 FUNCTION   : Maps the DASD allocation record on DASD for
              CYLINDER-BASED ALLOCATION MAPPING.
              (ECKD/CKD DASD with less than or equal to
              ALOCMAXCM cylinders.)
 LOCATED BY : The allocation record resides on CP formatted CKD
              and ECKD DASD on cylinder 0, head 0, record 4.  It
              exists only temporarily in storage.
 CREATED BY : ICKDSF when a CKD or ECKD DASD
              with less than or equal to ALOCMAXCM cylinders
              is formatted for CP use.
 DELETED BY : Exists in storage only until the in-storage
              representation of the allocation map (HCPVEXBK,
              HCPEXTBK) is built.
 RELOCATION CONSIDERATIONS : None
 COMMENTS   :
              If a CKD or ECKD DASD with more than ALOCMAXCM cylinders
              is formatted by ICKDSF, then an EXTENT-BASED ALLOCATION
              MAPPING is used.
              ALOC DSECT maps all CYLINDER-BASED ALLOCATION MAPPING.
              ALOCEXT DSECT maps all EXTENT-BASED ALLOCATION MAPPING.
 
 
  ALOC Control Block Content Top of page
 

 ALOC DSECT Top of page
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure ALOC DASD VOLUME ALLOCATION BLOCK 0000 0 Bitstring 1 ALOCNTS VOLUME TYPE CONTENTS THIS BYTE CONTAINS THE RESULTING BIT CONFIGURATION OBTAINED BY ORING ALL USE FLAGS THAT REPRESENT TYPE OF CYLINDERS ALLOCATED ON THIS VOLUME. 1... .... ALOCATED X'80' ALOCATED CYLINDER IS CURRENTLY IN USE THIS TYPE OF ALLOCATION SHOULD ONLY BE USED IN CONJUNCTION WITH THE TYPE 'DRCT' .1.. .... ALOCDRCT X'40' ALOCDRCT ALLOCATION TYPE 'DRCT' ..1. .... ALOCTDSK X'20' ALOCTDSK ALLOCATION TYPE 'TDSK' ...1 .... ALOCFULL X'10' ALOCFULL CYLINDER IS FULL NOTE- ALOCFULL is used only in combination with SPOL & PAGE .... 1... ALOCPERM X'08' ALOCPERM ALLOCATION TYPE 'PERM' .... ..1. ALOCSPOL X'02' ALOCSPOL ALLOCATION TYPE 'SPOL' Notes : ALOCSPOL == PGTSPOOL == PGUSPOOL == CPVTEMPS: 0001 1 Bitstring 1 ALOAVAIL AVAILABILITY OF TYPES 1... .... ALOCATED X'80' ALOCATED CYLINDER IS CURRENTLY IN USE THIS TYPE OF ALLOCATION SHOULD ONLY BE USED IN CONJUNCTION WITH THE TYPE 'DRCT' .1.. .... ALOCDRCT X'40' ALOCDRCT ALLOCATION TYPE 'DRCT' ..1. .... ALOCTDSK X'20' ALOCTDSK ALLOCATION TYPE 'TDSK' ...1 .... ALOCFULL X'10' ALOCFULL CYLINDER IS FULL NOTE- ALOCFULL is used only in combination with SPOL & PAGE .... 1... ALOCPERM X'08' ALOCPERM ALLOCATION TYPE 'PERM' .... ..1. ALOCSPOL X'02' ALOCSPOL ALLOCATION TYPE 'SPOL' Notes : ALOCSPOL == PGTSPOOL == PGUSPOOL == CPVTEMPS: 0002 2 Signed 2 ALOCYLS NUMBER OF CYLINDERS ON DEVICE Note that the high order bit in ALOCYLS (3rd byte of the allocation map) is reserved. It indicates whether or not the map is an extent-based map. In this cylinder-based form of the allocation map, the bit is off. 0004 4 Signed 4 * (2) Reserved for IBM use 000C 12 Bitstring 1 ALOSTAT VOLUME STATUS FLAG .1.. .... ALOCNFIL X'40' ALOCNFIL ALL 'CP SPACE' ON THIS VOLUME IS FORMATTED WITHOUT FILLER RECORDS 000D 13 Bitstring 1 ALOCODE Index into CPVOL list 000E 14 Signed 2 * RESERVED FOR FUTURE IBM USE 0010 16 Bitstring 8 ALOCMAP (0) START OF VARIABLE LENGTH DATA 1... .... ALOCATED X'80' ALOCATED CYLINDER IS CURRENTLY IN USE THIS TYPE OF ALLOCATION SHOULD ONLY BE USED IN CONJUNCTION WITH THE TYPE 'DRCT' .1.. .... ALOCDRCT X'40' ALOCDRCT ALLOCATION TYPE 'DRCT' ..1. .... ALOCTDSK X'20' ALOCTDSK ALLOCATION TYPE 'TDSK' ...1 .... ALOCFULL X'10' ALOCFULL CYLINDER IS FULL NOTE- ALOCFULL is used only in combination with SPOL & PAGE .... 1... ALOCPERM X'08' ALOCPERM ALLOCATION TYPE 'PERM' .... ..1. ALOCSPOL X'02' ALOCSPOL ALLOCATION TYPE 'SPOL' Notes : ALOCSPOL == PGTSPOOL == PGUSPOOL == CPVTEMPS: .... ...1 ALOCPAGE X'01' ALLOCATION TYPE 'PAGE' Notes : ALOCPAGE == PGTPAGE == PGUPAGE == CPVTEMPP: .... 11.. ALOCMDSK X'0C' Allocation type 'MDSK' ...1 11.. ALOCMORE X'1C' Allocation type 'MORE' 1... .... ALOCDRAN X'80' Device is permanently drained. .... .... ALOCUNDF X'00' Undefined allocation type; these cylinders/pages are ignored 0010 16 Bitstring 1 ALOCBYTE Allocation byte for a single cylinder 0011 17 Bitstring 1 ALOCNEXT Position of next allocation byte
 
 
  ALOC Storage Layout Top of page
 
          
*** ALOC - DASD VOLUME ALLOCATION BLOCK
*
*     +------+------+-------------+---------------------------+
*   0 |:CNTS |:AVAIL|  ALOCYLS    |///////////////////////////|
*     +------+------+-------------+------+------+-------------+
*   8 |///////////////////////////|:STAT |:CODE |/////////////|
*     +---------------------------+------+------+-------------+
*
*** ALOC - DASD VOLUME ALLOCATION BLOCK
          
*** Overlay for ALOCMAP in ALOC
*
*     +------+------+
*  10 |:CBYTE|:CNEXT| 12
*     +------+------+
*
*** Overlay for ALOCMAP in ALOC
 
 
  ALOC Cross Reference Top of page
 
 
Symbol         Dspl Value
-------------- ---- -----
ALOAVAIL       0001
ALOCATED       0000 80
ALOCATED       0001 80
ALOCATED       0010 80
ALOCBYTE       0010
ALOCDRAN       0010 80
ALOCDRCT       0000 40
ALOCDRCT       0001 40
ALOCDRCT       0010 40
ALOCFULL       0000 10
ALOCFULL       0001 10
ALOCFULL       0010 10
ALOCMAP        0010
ALOCMDSK       0010 0C
ALOCMORE       0010 1C
ALOCNEXT       0011
ALOCNFIL       000C 40
ALOCNTS        0000
ALOCODE        000D
ALOCPAGE       0010 01
ALOCPERM       0000 08
ALOCPERM       0001 08
ALOCPERM       0010 08
ALOCSPOL       0000 02
ALOCSPOL       0001 02
ALOCSPOL       0010 02
ALOCTDSK       0000 20
ALOCTDSK       0001 20
ALOCTDSK       0010 20
ALOCUNDF       0010 00
ALOCYLS        0002
ALOSTAT        000C
 
This information is based on z/VM 7.3.0 Last updated on 22 Jun 2022 at 15:57:41 EDT.
Copyright IBM Corporation, 1990, 2022