IBM: ALOC

Programming Interface Information: This information is NOT intended to be
used as Programming Interfaces of VM/ESA. It is to be used for diagnosis only.

ALOC

Prolog

Control Block Contents

ALOC DSECT

Storage Layout

Cross Reference (Contains links to field and bit definitions)

ALOC Prolog

 NAME       : HCPALOC
 DESCRIPTION: DASD VOLUME ALLOCATION BLOCK
 DSECT      : ALOC
 FUNCTION   : Maps the DASD allocation record on DASD for
              CYLINDER-BASED ALLOCATION MAPPING.
 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 is formatted for
              CP use.
 DELETED BY : Exists in storage only until the in-storage
              representation of the allocation map (HCPVEXBK,
              HCPEXTBK) is built.
 Comments   :
              ALOC DSECT maps all CYLINDER-BASED ALLOCATION MAPPING.
              ALOCEXT DSECT maps all EXTENT-BASED ALLOCATION MAPPING.

ALOC Control Block Content


ALOC DSECT
Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      ALOC           DASD VOLUME ALLOCATION BLOCK
     NOTES : ALOCFULL IS USED ONLY IN COMBINATION WITH SPOL & PAGE
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.
     NOTES : ALOCFULL IS USED ONLY IN COMBINATION WITH SPOL & PAGE
0001    1 Bitstring    1 ALOAVAIL       AVAILABILITY OF TYPES
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' 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
     NOTES : ALOCFULL IS USED ONLY IN COMBINATION WITH SPOL & PAGE
0010   16 Bitstring    8 ALOCMAP (0)    START OF VARIABLE LENGTH DATA
          1... ....      ALOCATED       X'80' CYLINDER IS CURRENTLY IN
                                        USE THIS TYPE OF ALLOCATION
                                        SHOULD ONLY BE USED IN
                                        CONJUNCTION WITH THE TYPE 'DRCT'
          .1.. ....      ALOCDRCT       X'40' ALLOCATION TYPE 'DRCT'
          ..1. ....      ALOCTDSK       X'20' ALLOCATION TYPE 'TDSK'
          ...1 ....      ALOCFULL       X'10' CYLINDER IS FULL
          .... 1...      ALOCPERM       X'08' ALLOCATION TYPE 'PERM'
          .... ..1.      ALOCSPOL       X'02' ALLOCATION TYPE 'SPOL'
                                        Notes : ALOCSPOL == PGTSPOOL ==
                                        PGUSPOOL == CPVTEMPS:
0010   16 Address      4 * (0)          (ALOCSPOL)))) IEV075 will result
                                        if ALOCSPOL NE PGTSPOOL @P3714FM
0010   16 Address      4 * (0)          (ALOCSPOL)))) IEV075 will result
                                        if ALOCSPOL NE PGUSPOOL @P3714FM
          .... ...1      ALOCPAGE       X'01' ALLOCATION TYPE 'PAGE'
                                        Notes : ALOCPAGE == PGTPAGE ==
                                        PGUPAGE == CPVTEMPP:
0010   16 Address      4 * (0)          LOCPAGE)))) IEV075 will result if
                                        ALOCPAGE NE PGTPAGE @P3714FM
0010   16 Address      4 * (0)          LOCPAGE)))) IEV075 will result if
                                        ALOCPAGE NE PGUPAGE @P3714FM
          .... 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

*** ALOC - DASD VOLUME ALLOCATION BLOCK
*
*     +------+------+-------------+---------------------------+
*   0 |:CNTS |:AVAIL|  ALOCYLS    |///////////////////////////|
*     +------+------+-------------+------+------+-------------+
*   8 |///////////////////////////|:STAT |:CODE |/////////////|
*     +---------------------------+------+------+-------------+
*  10
*
*** ALOC - DASD VOLUME ALLOCATION BLOCK
*** Overlay for ALOCMAP in ALOC
*
*     +------+------+
*  10 |:CBYTE|:CNEXT| 12
*     +------+------+
*
*** Overlay for ALOCMAP in ALOC