XLDBK | Back to Index page

| Prolog Control Block Contents XLDBK DSECT XLDENTRY 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.

XLDBK Prolog | Top of page

     NAME       : HCPXLDBK
     DESCRIPTION: eXtent List Definition BlocK.
     DSECT      : XLDBK
     FUNCTION   : The XLDBK is used for parameter passing for
                  diagnose X'244'.
     LOCATED BY : Rx      - Diagnose X'244' Rx register.
     CREATED BY : Created in the guest virtual machine's storage and
                  copied into a buffer page for CP use.
     DELETED BY : Deleted by the guest virtual machine.
     SERIALIZED : Guest Virtual Machine is responsible.
     RELOCATION CONSIDERATIONS : None
     COMMENTS   : This is a variable size block.
                  Use the following formula to figure out the actual
                  size of the control block.
                  XLDSIZE+(((nnn(XLDENTSZ))+7)/8)= number of doublewords
                  Where: XLDSIZE  - Header size in doublewords.
                  nnn      - Number of contiguous extent entries.
                  XLDENTSZ - Total size in bytes of one extent
                  entry.

XLDBK Control Block Content | Top of page

     XLDBK DSECT
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    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      XLDBK          eXtent List Definition BlocK.
    0000    0 Signed       4 XLDALET        ALET specifying the ad- dress
                                            space in which the next XLDBK
                                            resides.
    0004    4 Signed       4 XLDFWDPT       Forward pointer to next XLDBK.
    0008    8 Signed       4 XLDENTCT       Count of entries to be processed.
    000C   12 Signed       4 XLDRSVD        Reserved for IBM use. This field
                                            must contain zeroes.
    0010   16 Signed       4 XLDENTR1 (0)   Use XLDENTRY to map the entries
                                            that follow.
                 The following are used to determine the size of the
          header for this control block.                            .
              00000010       XLDLEN         *-XLDBK Length of the header in
                                            bytes.
              00000002       XLDSIZE        (XLDLEN+7)/8 Size of the header
                                            in doublewords.
                 The following DSECT represents an extent entry.

     XLDENTRY DSECT
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    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      XLDENTRY       eXtent List Definition BlocK.
    0000    0 Signed       4 XLDPRBN        This is the pool- relative block
                                            number assigned to the block
                                            specified for XLDMRBN.
    0004    4 Signed       4 XLDMRBN        Relative-block number of record
                                            on minidisk. Referenced from the
                                            start of the virtual minidisk
                                            starting with zero (0).
    0008    8 Signed       4 XLDCOUNT       Number of relative- block
                                            numbers(RBNs) for this extent.
    000C   12 Signed       2 XLDDEVNM       Virtual device number of device
                                            to be mapped.
    000E   14 Signed       2 *              Reserved for IBM use.
              00000010       XLDETLEN       *-XLDENTRY Length of the 1st
                                            entry.
              00000002       XLDESIZE       (XLDETLEN+7)/8 Size of this
                                            control block in doublewords.
    0010   16 Signed       4 XLDNXTET (0)   Next extent in list.
              00000100       XLDNMETP       4096/XLDETLEN The number of
                                            entries contained in a page.
              00001000       XLDSZETP       XLDETLEN*XLDNMETP Total storage
                                            size of all entries that can fit
                                            into a page.

XLDBK Storage Layout | Top of page

    *** XLDBK - eXtent List Definition BlocK.
    *
    *     +---------------------------+---------------------------+
    *   0 |         XLDALET           |         XLDFWDPT          |
    *     +---------------------------+---------------------------+
    *   8 |         XLDENTCT          |         XLDRSVD           |
    *     +---------------------------+---------------------------+
    *
    *** XLDBK - eXtent List Definition BlocK.

    *** XLDENTRY - eXtent List Definition BlocK.
    *
    *     +---------------------------+---------------------------+
    *   0 |         XLDPRBN           |         XLDMRBN           |
    *     +---------------------------+-------------+-------------+
    *   8 |         XLDCOUNT          |  XLDDEVNM   |/////////////|
    *     +---------------------------+-------------+-------------+
    *
    *** XLDENTRY - eXtent List Definition BlocK.

XLDBK Cross Reference | Top of page

    Symbol         Dspl Value
    -------------- ---- -----
    XLDALET        0000
    XLDCOUNT       0008
    XLDDEVNM       000C
    XLDENTCT       0008
    XLDENTR1       0010
    XLDESIZE       000E 00000002
    XLDETLEN       000E 00000010
    XLDFWDPT       0004
    XLDLEN         0010 00000010
    XLDMRBN        0004
    XLDNMETP       0010 00000100
    XLDNXTET       0010
    XLDPRBN        0000
    XLDRSVD        000C
    XLDSIZE        0010 00000002
    XLDSZETP       0010 00001000

This information is based on z/VM 7.2.0 Last updated on 24 Jun 2020 at 09:31:52 EDT.
Copyright IBM Corporation, 1990, 2020