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Programming Interface Information:
This information is NOT intended to be
used as Programming Interfaces of z/VM. |
DX2BK
Control Block Contents
DX2BK DSECT
Cross Reference (Contains links to field and bit definitions)
DX2BK Prolog
NAME : HCPDX2BK
DESCRIPTION: Minidisk extent index level 2.
DSECT : DX2BK
FUNCTION : A DX2BK contains the minidisk extents for a
minidisk-pool.
LOCATED BY : HCPDX1BK - DX1DX2Bk points to the DX2BK.
CREATED BY : HCPAMD44 When a Diagnose 244 is issued by the user.
DELETED BY : HCPAMD44 During an identify pool function the
previous DX1BK will be deleted if any.
HCPMSMDP During storage reset operation.
COMMENTS :
DX2BK Control Block Content
DX2BK DSECT
Hex Dec Type/Val Lng Label (dup) Comments
---- ---- --------- ---- -------------- --------
0000 0 Structure DX2BK Minidisk extent index level 2.
Each entry in this table represents one minidisk extent. This is the
first part of an entry which is split into four parts. This part
contains the pool-relative-block number start and end for the extent.
0000 0 Signed 4 DX2PRBNS Pool-Relative-block number (PRBN)
start for this minidisk extent.
0004 4 Signed 4 DX2PRBNE PRBN end for this minidisk
extent.
00000008 DX21ENT4 *-DX2PRBNS Used to get length of
this entry.
0008 8 Dbl-Word 8 DX2PRBNX (127) Next entry in table
This is the second part of an entry which is split into four parts.
This part contains the device-relative-block number start and end for
the extent.
0400 1024 Signed 4 DX2DRBNS Device-Relative-block number
(DRBN) start for this minidisk
extent.
0404 1028 Signed 4 DX2DRBNE DRBN end for this minidisk
extent.
00000008 DX22ENT4 *-DX2DRBNS Used to get length of
this entry.
0408 1032 Dbl-Word 8 DX2DRBNX (127) Next entry in table.
This is the third part of an entry which is split into four parts. This
part contains the minidisk's starting and ending cylinder or block
numbers on the physical device.
0800 2048 Signed 4 DX2MEXT (0) Minidisk extent information
0800 2048 Signed 4 DX2MSEXT Minidisk starting cylinder (CKD/
ECKD) or 512-byte block (FBA)
0804 2052 Signed 4 DX2MEEXT Minidisk ending cylinder (CKD/
ECKD) or 512-byte block (FBA)
00000008 DX23ENT4 *-DX2MEXT Used to get length of
this entry.
0808 2056 Dbl-Word 8 DX2MCYNX (127) Next entry in table.
This is the fourth part of an entry which is split into four parts.
This part contains the EXPBK or MEXBK address, status field and the
virtual device number.
0C00 3072 Address 4 DX2EXPBK Address of the EXPBK or MEXBK for
these PRBN.
0C04 3076 Signed 2 DX2VDEVN Virtual device number for the
minidisk.
0C06 3078 Bitstring 1 DX2STAT Status byte
1... .... DX2INVLD X'80' Indicates this extent is
invalid.
.1.. .... DX2READO X'40' Indicates that this extent
is on a read only DASD. If this
extent is mapped the PTE should
have the page protect bit set on.
..1. .... DX2FBA X'20' Indicates that this
minidisk extent resides on an FBA
device
0C07 3079 Bitstring 1 * Reserved for IBM use.
00000008 DX24ENT4 *-DX2EXPBK Used to get length of
this entry.
0C08 3080 Dbl-Word 8 DX2EXPNX (127) Next entry in table.
The following equates are used to get the number of entries that will
fit in a page. DX2ETBSZ is the total size in bytes of all the parts of
an entry. DX2NMENT is the total number of entries that will fit in a
page.
00000020 DX2ETBSZ (DX21ENT4+DX22ENT4+DX23ENT4+DX24E
NT4)
00000080 DX2NMENT 4096/DX2ETBSZ
If the number of entries that can be contained in this control block
decreases to 127 or lower then HCPDX1BK will have to increase to two or
more contiguous pages. Therefore the following statement will fail when
the number of entries decreases to 127 or lower.
DX2BK Storage Layout
*** DX2BK - Minidisk extent index level 2.
*
* +---------------------------+---------------------------+
* 0 | DX2PRBNS | DX2PRBNE |
* +---------------------------+---------------------------+
* 8 | |
* = DX2PRBNX =
* | |
* +---------------------------+---------------------------+
* 400 | DX2DRBNS | DX2DRBNE |
* +---------------------------+---------------------------+
* 408 | |
* = DX2DRBNX =
* | |
* +---------------------------+---------------------------+
* 800 | DX2MSEXT | DX2MEEXT |
* +---------------------------+---------------------------+
* 808 | |
* = DX2MCYNX =
* | |
* +---------------------------+-------------+------+------+
* C00 | DX2EXPBK | DX2VDEVN |:STAT |//////|
* +---------------------------+-------------+------+------+
* C08 | |
* = DX2EXPNX =
* | |
* +-------------------------------------------------------+
*1000
*
*** DX2BK - Minidisk extent index level 2.
DX2BK Cross Reference
Symbol Dspl Value -------------- ---- ----- DX2DRBNE 0404 DX2DRBNS 0400 DX2DRBNX 0408 DX2ETBSZ 0C08 00000020 DX2EXPBK 0C00 DX2EXPNX 0C08 DX2FBA 0C06 20 DX2INVLD 0C06 80 DX2MCYNX 0808 DX2MEEXT 0804 DX2MEXT 0800 DX2MSEXT 0800 DX2NMENT 0C08 00000080 DX2PRBNE 0004 DX2PRBNS 0000 DX2PRBNX 0008 DX2READO 0C06 40 DX2STAT 0C06 DX2VDEVN 0C04 DX21ENT4 0004 00000008 DX22ENT4 0404 00000008 DX23ENT4 0804 00000008 DX24ENT4 0C07 00000008
Last updated on 5 Jun 2001 at 13:30:52 EDT.
Copyright IBM Corporation, 1990, 2001