XBLBK - 32-bit CP - V4R4.0

Programming Interface Information: This information is NOT intended to be used as Programming Interfaces of z/VM.

#### XBLBK

Prolog

Control Block Contents
XBLBK DSECT

Storage Layout

Cross Reference (Contains links to field and bit definitions)

#### XBLBK Prolog

     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.
     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

#### XBLBK DSECT

    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

    *** 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

    Symbol         Dspl Value
    -------------- ---- -----
    XBLDATA        0010
    XBLDEVCT       0008
    XBLHDRSZ       000C 00000002
    XBLRBFAD       0010
    XBLRBFCT       000C
    XBLRBSIZ       0010 00000004

This information is based on z/VM V4R4.0. Last updated on 29 Jul 2003 at 16:38:13 EDT.
Copyright IBM Corporation, 1990, 2003