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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. |
ALOCEXT
Cross Reference (Contains links to field and bit definitions)
ALOCEXT Prolog
Name : HCPALOC
Description: DASD allocation record mapping for
EXTENT-BASED ALLOCATION MAPPING.
DSECT : ALOCEXT
Function : Maps the DASD allocation record for system owned
volumes with EXTENT-BASED ALLOCATION MAPPING.
Located by : n/a
exists only temporarily in storage,
resides in block numbers 3 and 4 of
an FBA DASD formatted for CP use
For CKD and ECKD DASD, resides on
cylinder 0, head 0, record 4.
Created by : ICKDSF
when a DASD is formatted for ESA
CP use
Deleted by : n/a
exists in storage only until the in
storage allocation map is built
Notes :
The FBA allocation record resides on FBA volumes formatted
for CP use in the reserved pages, blocks 3 & 4. There are
two versions of the FBA allocation record, one for volumes
formatted for 370 CP (which ESA CP can use), and one for
volumes formatted for ESA CP. The two versions map almost
exactly the same. The ESA version has an indicator that
this is an extent-based allocation map as well as ESA
allocation types.
Volumes which are formatted for ESA CP use are marked by
the presence of the string "CPVOL" in the volume owner
area of the OS volume label record (block 1).
FBA volumes which are formatted for 370 CP use are marked
by the presence of the string "CP370" in the volume owner
area of the OS volume label record (block 1). FBA volumes
formatted for 370 CP are usable by ESA CP without
reformatting.
The layout of the blocks in the reserved pages of FBA
volumes is:
0 - IPL record
1 - OS VOL1 volume label record
2 - VTOC - OS FORMAT 4 & FORMAT 5 labels
3-4 - Allocation Record extent map
5-12 - Initialized to 0
13-31 - Reserved, initialized to 0.
Note that the length of the allocation record is variable
depending on the number of extents. The overall length of
the allocation record is determined by multiplying the
number of entries (found in bytes 3-4 of the first entry)
by the length of an entry, and adding one (the next byte
after the last entry is marked with X'FF').
The allocation type values for all DASD formatted for ESA
CP are the same for all types of DASD (CKD, ECKD, FBA).
ALOCEXT Control Block Content
ALOCEXT DSECT
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure ALOCEXT DASD allocation record mapping for 0000 0 Bitstring 12 ALOCEENT (0) Extent map entry 0000 0 Bitstring 1 ALOCETYP Extent allocation type .... .... ALO370TE X'00' 370 FBA allocation type 'TEMP' .... ...1 ALO370PE X'01' 370 FBA allocation type 'PERM' .... ..1. ALO370TD X'02' 370 FBA allocation type 'TDSK' .... .1.. ALO370DR X'04' 370 FBA allocation type 'DRCT' 1... .1.. ALO370AD X'84' 370 FBA type in-use DRCT space .... 1... ALO370PA X'08' 370 FBA allocation type 'PAGE' ...1 .... ALO370DU X'10' 370 FBA allocation type 'DUMP' ...1 .1.. ALO370OV X'14' 370 FBA allocation type 'OVRD' ...1 11.. ALO370AO X'1C' 370 FBA type in-use OVRD space 0001 1 Bitstring 1 ALOCECNT Volume allocation contents - contains all of the extent map entry ALOCETYP bytes ORed together (valid only in first extent map entry on ESA formatted volumes, not valid for volumes formatted for 370) 0002 2 Signed 2 ALOCEECT Count of allocation extent map entries. Also, has indicator that this is an extent-based map. (Both count and indicator are valid only in 1st extent map entry.) 0004 4 Signed 4 ALOCESTR Extent start slot number FBA Extent start cyl number E/CKD 0008 8 Signed 4 ALOCEEND Extent end slot number FBA Extent end cyl number E/CKD 000C 12 Bitstring 1 ALOCENXT (0) Next extent entry 1111 1111 ALOCEND X'FF' Marks the end of the allocation map 00000055 ALOCFMXX 85 Maximum number of extents allowed in one allocation map (FBA) 00000154 ALOCEMXX 340 Maximum number of extents allowed in one allocation map (E/CKD) 0000000C ALOCEENL *-ALOCEENT Length of an extent entry 0002 2 Bitstring 1 ALOCEFLG Holds flag indicating this is the extent-based allocation map. Note that the other bits in this byte are NOT available to use as this field overlaps ALOCEECT. 1... .... ALOCEXTM X'80' Indicates this is the extent based allocation map. 0003 3 Bitstring 1 * Do not use..Part of remap.
ALOCEXT Storage Layout
*** ALOCEXT - DASD allocation record mapping for * * +------+------+-------------+---------------------------+ * 0 |:CETYP|:CECNT| ALOCEECT | ALOCESTR | * +------+------+-------------+---------------------------+ * 8 | ALOCEEND | * +---------------------------+ * *** ALOCEXT - DASD allocation record mapping for *** Overlay for ALOCEECT in ALOCEXT * * +------+------+ * 0 ... 2 |:CEFLG|//////| 4 * +------+------+ * *** Overlay for ALOCEECT in ALOCEXT
ALOCEXT Cross Reference
(contains links to field and bit definitions)Symbol Dspl Value -------------- ---- -----ALOCECNT 0001
ALOCEECT 0002
ALOCEEND 0008
ALOCEENL 000C 0000000C
ALOCEENT 0000
ALOCEFLG 0002
ALOCEMXX 000C 00000154
ALOCEND 000C FF
ALOCENXT 000C
ALOCESTR 0004
ALOCETYP 0000
ALOCEXTM 0002 80
ALOCFMXX 000C 00000055
ALO370AD 0000 84
ALO370AO 0000 1C
ALO370DR 0000 04
ALO370DU 0000 10
ALO370OV 0000 14
ALO370PA 0000 08
ALO370PE 0000 01
ALO370TD 0000 02
ALO370TE 0000 00
Last updated on 1 Oct 1999 at 08:39:43 EDT.
Copyright IBM Corporation, 1990, 1999