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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. |
EXTBK
Cross Reference (Contains links to field and bit definitions)
EXTBK Prolog
NAME : HCPEXTBK
DESCRIPTION: Extent Block
DSECT : EXTBK
FUNCTION : Describes a group of contiguous cylinders or slots
on a CP-owned DASD containing the same allocation type.
LOCATED BY : VEXPGEXT
VEXSPEXT
VEXTDEXT
VEXDREXT
VEXPEEXT
VEX1SEXT
EXTMYEXT
EXTANYEX
CREATED BY : HCPRDX when a CP-owned device is attached
to the system
DELETED BY : HCPRDD when a CP-owned device is detached
from the system
REFERENCES : HCPMSABK - Map for Slot Allocation
HCPMDISK - Minidisk block
SERIALIZED : Allocation locks
NOTES : EXTBKs of type PERM use only the following fields:
EXTVEXBK, EXTSTART, EXTEND, EXTANYEX, and EXTMYEXT.
EXTBKs are not created for type PARM or UNDF, as
they are not needed in the internal representation
of the allocation map.
EXTBK Control Block Content
EXTBK DSECT
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure EXTBK Extent Block 0000 0 Signed 4 EXTVEXBK Pointer back to VEXBK The following 2 fields vary in units depending on the type of device. 0004 4 Signed 4 EXTSTART Starting cylinder (CKD/ECKD) or slot (FBA) for this extent 0008 8 Signed 4 EXTEND Ending cylinder (CKD/ECKD) or slot (FBA) for this extent 000C 12 Signed 4 EXTINUSE Number in use in this EXTBK. In cylinders for E/CKD TDSK and DRCT extents. In slots for E/CKD PAGE and SPOL extents and for all FBA extents. Not used for PERM. 0010 16 Signed 4 EXTHIGH Highest slot or cylinder in use in this extent. Used only by TDSK and DRCT extents. This number is relative to the start of the volume. Query Alloc will actually report this number relative to the start of the extent. 0014 20 Signed 4 EXTSTRCT Pointer to a structure which further describes what parts of the extent are in use. For PAGE and SPOL this points to a MSABK. For TDSK, this points to an MDISK block. Equals 0 for DRCT and PERM extents. 0018 24 Signed 4 EXTANYEX Pointer to next extent on volume of any type. (for Q ALLOC MAP) 001C 28 Signed 4 EXTMYEXT Pointer to next extent on volume of this type 0020 32 Signed 4 EXTSTSLT Slot number of first slot in EXTBK. Same as EXTSTART for FBA devices. 0024 36 Signed 4 EXTENSLT Slot number of last slot in EXTBK. Same as EXTEND for FBA devices. 0028 40 Signed 4 EXTFREE Number of free slots in this extent when stopped allocating from this extent. Used to determine if need to get new CASBKs. 002C 44 Signed 4 EXTSLOTS Number of slots in this extent 0030 48 Bitstring 1 EXTTYPE Allocation type for this extent 0031 49 Bitstring 1 EXTFLAG Flag byte 1... .... EXTFULL X'80' Indicates entire extent is in use .1.. .... EXTLOG1 X'40' This EXTBK is the first in a series of EXTBKs associated with 1 physical extent on the DASD ..1. .... EXTLOGEX X'20' This EXTBK belongs to a series of EXTBKs associated with 1 physical extent on the DASD. This EXTBK is not the first EXTBK in the series. 0032 50 Signed 2 * Reserved for IBM use 00000007 EXTSIZE (*-EXTBK+7)/8 Size, in doublewords, of EXTBK 00000034 EXTSIZEB *-EXTBK Size of EXTBK in bytes 0000004E EXTPRPG (4096-24)/EXTSIZEB Maximum number of EXTBKs per page
EXTBK Storage Layout
*** EXTBK - Extent Block * * +---------------------------+---------------------------+ * 0 | EXTVEXBK | EXTSTART | * +---------------------------+---------------------------+ * 8 | EXTEND | EXTINUSE | * +---------------------------+---------------------------+ * 10 | EXTHIGH | EXTSTRCT | * +---------------------------+---------------------------+ * 18 | EXTANYEX | EXTMYEXT | * +---------------------------+---------------------------+ * 20 | EXTSTSLT | EXTENSLT | * +---------------------------+---------------------------+ * 28 | EXTFREE | EXTSLOTS | * +------+------+-------------+---------------------------+ * 30 |:TYPE |:FLAG |/////////////| 34 * +------+------+-------------+ * *** EXTBK - Extent Block
EXTBK Cross Reference
(contains links to field and bit definitions)Symbol Dspl Value -------------- ---- -----EXTANYEX 0018
EXTEND 0008
EXTENSLT 0024
EXTFLAG 0031
EXTFREE 0028
EXTFULL 0031 80
EXTHIGH 0010
EXTINUSE 000C
EXTLOGEX 0031 20
EXTLOG1 0031 40
EXTMYEXT 001C
EXTPRPG 0032 0000004E
EXTSIZE 0032 00000007
EXTSIZEB 0032 00000034
EXTSLOTS 002C
EXTSTART 0004
EXTSTRCT 0014
EXTSTSLT 0020
EXTTYPE 0030
EXTVEXBK 0000
Last updated on 3 Aug 1999 at 11:55:15 EDT.
Copyright IBM Corporation, 1990, 1999