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Programming Interface Information:
This information is NOT intended to be
used as Programming Interfaces of z/VM. |
MEXBK
Control Block Contents
MEXBK DSECT
MEXENTRY DSECT
Cross Reference (Contains links to field and bit definitions)
MEXBK Prolog
NAME : HCPMEXBK
DESCRIPTION: MULTIPLE EXPOSURE BLOCK
DSECT : MEXBK
FUNCTION : CONTAINS THE NECESSARY INFORMATION TO FIND EACH EXPOSURE
FOR MULTIPLE EXPOSURE DEVICES.
LOCATED BY : RDEVEXPB FIELD OF RDEV - POINTER TO MEXBK
CREATED BY : HCPRDAAT - DURING ATTACH OF A MULTIPLE EXPOSURE DASD DEVICE
DELETED BY : HCPRDADT - DURING DETACH OF A MULTIPLE EXPOSURE DASD DEVICE
MEXBK Control Block Content
MEXBK DSECT
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure MEXBK MULTIPLE EXPOSURE BLOCK 0000 0 Bitstring 1 MEXCTEXP Count of exposure blocks. 0001 1 Bitstring 1 * Reserved for IBM use. This is information for multiple exposure blocks. This information indicates what exposure to use next for the reads or writes. 0002 2 Bitstring 6 MEXRDWRI (0) 0002 2 Bitstring 1 MEXFRDEX First read exposure 0003 3 Bitstring 1 MEXLRDEX Last read exposure 0004 4 Bitstring 1 MEXCREAD Current available read exposure These are the write exposures. 0005 5 Bitstring 1 MEXFWREX First available write exposures 0006 6 Bitstring 1 MEXLWREX Last write exposure 0007 7 Bitstring 1 MEXCWRIT Current available write exposure 0008 8 Address 4 MEX1STEX Address of location of the first exposure block. 000C 12 Signed 4 * Reserved for IBM use. 0010 16 Bitstring 16 MEXEXPBK (0) Address of the first exposure block. 0010 16 Address 4 * Place for exposure block address. 00000004 MEXENTLN *-MEXEXPBK Length of an entry. 0014 20 Address 4 MEXNXTEX (3) Place for three exposure block addresses. 00000004 MEXEXPEC L'MEXEXPBK/MEXENTLN Count of entries in the exposure block field MEXEXPBK. 00000020 MEXLEN *-MEXBK 00000004 MEXSIZE (MEXLEN+7)/8 Number of doublewords. Use this to DSECT the read and write areas MEXFRDEX, MEXLRDEX, MEXCRDIT and MEXFWREX, MEXLWREX, MEXCWRIT.
MEXENTRY DSECT
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure MEXENTRY MULTIPLE EXPOSURE BLOCK 0000 0 Bitstring 1 MEXFIRST First available write exposures 0001 1 Bitstring 1 MEXLAST Last write exposure 0002 2 Bitstring 1 MEXCURR Current available write exposure
MEXBK Storage Layout
*** MEXBK - MULTIPLE EXPOSURE BLOCK * * +------+------+------+------+------+------+------+------+ * 0 |:CTEXP|//////|:FRDEX|:LRDEX|:CREAD|:FWREX|:LWREX|:CWRIT| * +------+------+------+------+------+------+------+------+ * 8 | MEX1STEX |///////////////////////////| * +---------------------------+---------------------------+ * 10 |///////////////////////////| MEXNXTEX | * +---------------------------+ | * | | * +-------------------------------------------------------+ * 20 * *** MEXBK - MULTIPLE EXPOSURE BLOCK *** MEXENTRY - MULTIPLE EXPOSURE BLOCK * * +------+------+------+ * 0 |:FIRST|:LAST |:CURR | 3 * +------+------+------+ * *** MEXENTRY - MULTIPLE EXPOSURE BLOCK
MEXBK Cross Reference
Symbol Dspl Value -------------- ---- ----- MEXCREAD 0004 MEXCTEXP 0000 MEXCURR 0002 MEXCWRIT 0007 MEXENTLN 0010 00000004 MEXEXPBK 0010 MEXEXPEC 0014 00000004 MEXFIRST 0000 MEXFRDEX 0002 MEXFWREX 0005 MEXLAST 0001 MEXLEN 0014 00000020 MEXLRDEX 0003 MEXLWREX 0006 MEXNXTEX 0014 MEXRDWRI 0002 MEXSIZE 0014 00000004 MEX1STEX 0008
This information is based on z/VM V4R1.0.
Last updated on 5 Jun 2001 at 14:23:01 EDT.
Copyright IBM Corporation, 1990, 2001