XBLBK Back to Index page
 
Prolog 
Control Block Contents 
   XBLBK DSECT
Storage Layout 
Cross Reference (Contains links to field and bit definitions)
Programming Interface Information:
This information is NOT intended to be
used as Programming Interfaces of z/VM.


  XBLBK Prolog Top of page
 
 NAME       : HCPXBLBK
 DESCRIPTION: XA buffer list block.
 DSECT      : XBLBK
 FUNCTION   : This block is used to keep track of the real buffers
              that contain virtual device information.
 LOCATED BY : Addressability is established when obtaining
              FREE storage. The block is not anchored anywhere.
 CREATED BY : HCPIIR when saving the virtual device information.
              - HCPNSE when restoring the virtual device information.
 DELETED BY : HCPNSE will return the block to FREE storage.
 RELOCATION CONSIDERATIONS : None
 COMMENTS   : This is a variable length block. The size is the header,
              plus one-half the number of real page buffers, plus one.
 
 
  XBLBK Control Block Content Top of page
 

 XBLBK DSECT Top of page
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure XBLBK XA buffer list block. 0000 0 Bitstring 8 * Reserved for future IBM use. 0008 8 Signed 4 XBLDEVCT COUNT OF THE NUMBER OF DEVICES. 000C 12 Signed 4 XBLRBFCT COUNT OF REAL BUFFER ADDRESSES. 00000002 XBLHDRSZ (((*-XBLBK)+7)/8) This is the header size in DW. 0010 16 Signed 4 XBLDATA (0) Start of variable length data. 0010 16 Signed 4 XBLRBFAD The first real buffer address starts here. 00000004 XBLRBSIZ (*-XBLRBFAD) This is the size of an entry for a real buffer.
 
 
  XBLBK Storage Layout Top of page
 
          
*** XBLBK - XA buffer list block.
*
*     +-------------------------------------------------------+
*   0 |///////////////////////////////////////////////////////|
*     +---------------------------+---------------------------+
*   8 |         XBLDEVCT          |         XBLRBFCT          |
*     +---------------------------+---------------------------+
*
*** XBLBK - XA buffer list block.
          
*** Overlay for XBLDATA in XBLBK
*
*     +---------------------------+
*  10 |         XBLRBFAD          | 14
*     +---------------------------+
*
*** Overlay for XBLDATA in XBLBK
 
 
  XBLBK Cross Reference Top of page
 
 
Symbol         Dspl Value
-------------- ---- -----
XBLDATA        0010
XBLDEVCT       0008
XBLHDRSZ       000C 00000002
XBLRBFAD       0010
XBLRBFCT       000C
XBLRBSIZ       0010 00000004
 
This information is based on z/VM 7.3.0 Last updated on 22 Jun 2022 at 15:58:07 EDT.
Copyright IBM Corporation, 1990, 2022