IBM: XLDBK

Programming Interface Information: This information is NOT intended to be
used as Programming Interfaces of VM/ESA. It is to be used for diagnosis only.

XLDBK

Prolog

Control Block Contents

XLDBK DSECT

XLDENTRY DSECT

Storage Layout

Cross Reference (Contains links to field and bit definitions)

XLDBK Prolog

 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.
 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


XLDBK DSECT
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
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

*** XLDBK - eXtent List Definition BlocK.
*
*     +---------------------------+---------------------------+
*   0 |         XLDALET           |         XLDFWDPT          |
*     +---------------------------+---------------------------+
*   8 |         XLDENTCT          |         XLDRSVD           |
*     +---------------------------+---------------------------+
*  10 |                                                       |
*     =                       XLDENTR1                        =
*     |                                                       |
*     +-------------------------------------------------------+
*
*** XLDBK - eXtent List Definition BlocK.
*** XLDENTRY - eXtent List Definition BlocK.
*
*     +---------------------------+---------------------------+
*   0 |         XLDPRBN           |         XLDMRBN           |
*     +---------------------------+-------------+-------------+
*   8 |         XLDCOUNT          |  XLDDEVNM   |/////////////|
*     +---------------------------+-------------+-------------+
*  10 |                                                       |
*     =                       XLDNXTET                        =
*     |                                                       |
*     +-------------------------------------------------------+
*
*** XLDENTRY - eXtent List Definition BlocK.