BITMP Back to Index page
Control Block Contents 
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.

  BITMP Prolog Top of page
 DESCRIPTION: Bit Map Control Block
 FUNCTION   : The Bit Map Control Block contains fields that control
              access to the bits, pointers to the bits, and other
              useful stuff.
 LOCATED BY : R2 at entry to HCPBIT routines points to a full
              word that points to the BITMP.
 SERIALIZED : Changes to the contents of bit maps need not be done
              under the control of the BITMP lock, because
              Compare-and-Swap is used to change the bits and the
              pointers to the bits.  However, if serialization is
              needed, the users of the bit maps should call the
              HCPBIT entry points AS, AX, RS, RX, SX, etc., which
              call the analogous HCPLCK entry points for control
              over the BITMP lock.
 RELOCATION CONSIDERATIONS : This control block is relocated as part of a live
              guest relocation (LGR).  The bits and fields that
              need to be relocated are defined in the
              corresponding LGRBITMP COPY file.  Whenever changes
              are made to this control block, consideration must
              be given to any effects these changes will have on
              a relocation.  If any new fields or bits are
              defined, they may need to be relocated.  If
              existing bits or fields are changed, corresponding
              modifications may be required in the LGR version of
              this control block.  Consider also the effects of
              these changes on a relocation involving a back-level
              release of CP.
  BITMP Control Block Content Top of page

 BITMP DSECT Top of page
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure BITMP Bit Map Control Block This portion of the BITMP is fixed length. The final size of the BITMP depends on how many pointers are actually stored at BITMPPTR. 00000000 BITMPFXD * Fixed portion of the BITMP 0000 0 Dbl-Word 8 BITMPLCK (3) The BITMP lock 0018 24 Signed 4 BITMPMAX The max bit number allowed 001C 28 Signed 4 BITMPPGS How many pointers at BITMPPTR 00000020 BITMPFSZ *-BITMP Size of fixed portion of BITMP expressed in bytes. 0020 32 Address 4 BITMPPTR (0) Start of variable length data. Pointers to pages of bits. The upper bound of the subscript for this array is contained in BITMPPGS.
  BITMP Storage Layout Top of page
*** BITMP - Bit Map Control Block
*     +-------------------------------------------------------+
*   0 |                                                       |
*     =                       BITMPLCK                        =
*     |                                                       |
*     +---------------------------+---------------------------+
*  18 |         BITMPMAX          |         BITMPPGS          |
*     +---------------------------+---------------------------+
*** BITMP - Bit Map Control Block
  BITMP Cross Reference Top of page
Symbol         Dspl Value
-------------- ---- -----
BITMPFSZ       001C 00000020
BITMPFXD       0000 00000000
BITMPLCK       0000
BITMPMAX       0018
BITMPPGS       001C
BITMPPTR       0020
This information is based on z/VM 6.3.0 Last updated on 22 May 2013 at 13:53:54 EDT.
Copyright IBM Corporation, 1990, 2013