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Hex Dec Type/Val Lng Label (dup) Comments
---- ---- --------- ---- -------------- --------
0000 0 Structure DXDA Define Extent data area
0000 0 Bitstring 32 DXDAREA (0) Define extent data area
Byte 0 (Mask byte)
Although defined as BITs, the contents of the
mask byte are, architecturally, multiple codes.
0000 0 Bitstring 1 DXDMASK Mask
11.. .... DXDMWC X'C0' DXDMWC Mask byte, bits 0
and 1 ------- Codes for use with
DXDMWC
.... .... DXDMWCH0 X'00' DXDMWCH0 Permit all write
operations except write HA and
Rec 0
.1.. .... DXDMWCIW X'40' DXDMWCIW Inhibit all write
operations
1... .... DXDMWCIF X'80' DXDMWCIF Permit update
write operations only
11.. .... DXDMWCPA X'C0' DXDMWCPA Permit all write
commands -------
..1. .... DXDMNU X'20' Mask byte, bit 2 (not used)
...1 1... DXDMSC X'18' Mask byte, bits 3 and 4
------- Codes for use with DXDMSC
.... .... DXDMSCPA X'00' Permit all seek commands
.... 1... DXDMSCCH X'08' Permit seek cyl/head
commands
...1 .... DXDMSCH X'10' Permit seek head commands
...1 1... DXDMSCIS X'18' Inhibit all seek commands
-------
.... .11. DXDMAA X'06' Mask byte, bits 5 and 6
------- Codes for use with DXDMAA
.... .... DXDMAAN X'00' Normal authorization
.... ..1. DXDMAADE X'02' Device support
authorization
.... .1.. DXDMAADI X'04' Diagnostic authorization
.... .11. DXDMAADR X'06' Device support
authorization with inhibit data
check correction and retry
-------
.... ...1 DXDMPCI X'01' Mask byte, bit 7
Byte 1 (Attribute byte)
This byte, like the mask byte, contains multiple
codes. See the explaination of the mask byte for
possible ways to manipulate the codes.
0001 1 Bitstring 1 DXDATTR Global Attributes
11.. .... DXDAAM X'C0' DXDAAM Attributes byte,
bits 0 and 1 ------- Codes for
use with DXDAAM
11.. .... DXDAAME X'C0' DXDAAME ECKD mode --------
..1. .... DXDACMON X'20' CKD conversion mode on
...1 11.. DXDASO X'1C' Attributes byte, bits 3, 4,
and 5 ------- Codes for use with
DXDASO
.... .... DXDASONR X'00' Normal cache replacement
.... .1.. DXDASOBC X'04' Bypass cache
.... 1... DXDASOIL X'08' Inhibit cache loading
.... 11.. DXDASOSA X'0C' Sequential access
...1 .1.. DXDARECA X'14' Record access
.... 1... DXDARECN X'08' Inverse of record access
-------
.... ..1. DXDCFW X'02' Cache fast write
.... ...1 DXDDFW X'01' DASD fast write
Bytes 2 and 3 (block size)
0002 2 Bitstring 2 DXDBLKSZ Block size
Bytes 4 through 7 (global attributes extended
and reserved)
0004 4 Bitstring 4 DXDZEROS (0) Reserved on some devices
0004 4 Bitstring 3 *
0007 7 Bitstring 1 DXDGLAE Global attributes extended
.1.. .... DXDRDF X'40' DXDRDF Regular data format
mode
.... 1... DXDTSVAL X'08' DXDTSVAL Time stamp valid
.... .1.. DXDSTDR0 X'04' DXDSTDR0 Standard R0 Format
.... ..1. DXDEXPRM X'02' DXDEXPRM Extended Parameter
Bit
Bytes 8 through 11 (beginning extent address)
0008 8 Bitstring 4 DXDBXADR (0) Beg extent address, CCHH
0008 8 Bitstring 2 DXDBXCC CC of beginning CCHH
000A 10 Bitstring 2 DXDBXHH HH of beginning CCHH
Bytes 12 through 15 (ending extent address)
000C 12 Bitstring 4 DXDEXADR (0) Ending extent address, CCHH
000C 12 Bitstring 2 DXDEXCC CC of ending CCHH
000E 14 Bitstring 2 DXDEXHH HH of ending CCHH
00000010 DXDNXRCL *-DXDAREA No XRC Support data
length
Bytes 16 through 23 (time stamp)
0010 16 Bitstring 8 DXDTSTAM Time stamp
00000018 DXDXRCL *-DXDAREA XRC Support data length
Bytes 24 through 31
CHECK TO SEE IF OTHER BITS SHOULD BE ADDED
0018 24 Bitstring 1 DXDEPARM Global attributes extended
..1. .... DXDEB27 X'20' DXDEB27 Byte 27 has
records/track
0019 25 Bitstring 1 DXDPRIOR Priority of IO
001A 26 Bitstring 1 DXDXRC XRC/CH extender
001B 27 Bitstring 1 DXDRCDS Byte 27 - records per track
001C 28 Bitstring 4 DXDRSRVD Reserved for hardware use
Length equates
00000020 DXDBSIZE *-DXDAREA Size of DXDA in bytes
00000004 DXDSIZE ((*-DXDAREA)+7)/8 Size of DXDA in
DWs
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