IDSBK | Back to Index page

| Prolog Control Block Contents IDSBK DSECT IDSEGENT DSECT IDSLTENT 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.

IDSBK Prolog | Top of page

     NAME       : HCPIDSBK
     DESCRIPTION: ISFC ID segment table
     DSECT      : IDSBK
     FUNCTION   : A simple segment-page table to locate address of a
                  PTHBK or generate a unique ID for an ISFC resource.
     LOCATED BY : HCPBTB    contains an anchor for each table.
     CREATED BY : HCPBTB    as new entries are needed.
     DELETED BY : HCPBTB    as old entries are discarded.
     SERIALIZED : The ISFC global lock (HCPBDSGL).
     RELOCATION CONSIDERATIONS : None

IDSBK Control Block Content | Top of page

     IDSBK DSECT
    Top of page

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      IDSBK          ISFC ID segment table
    0000    0 Signed       4 IDSCOUNT       Total count of IDs in this table
    0004    4 Signed       4 IDSHMARK       High water mark for this table
    0008    8 Dbl-Word     8 *              Reserved The value of
                                            (IDSMAXSG*IDSEGBLN) for BLOCKMAP
                                            is 64*8 = 512
    0010   16 Bitstring  512 IDSSTART       Reserve IDSEGENT space
              00000042       IDSSIZE        (*-IDSBK+7)/8 Size of IDSBK in
                                            doublewords
          FUNCTION   :
            This is the format for a single 'Segment Entry' in
            the IDSBK.
          LOCATED BY :
            IDSSTART  contains IDSEGENT entries.

     IDSEGENT DSECT
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    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      IDSEGENT       ISFC ID segment table
    0000    0 Signed       4 IDSEGCNT       Count of IDs in this segment
    0004    4 Address      4 IDSEGADD       Address of segment page
              00000008       IDSEGBLN       *-IDSEGENT Length of segment
                                            entry in bytes
          FUNCTION   :
            This is the format for a single 'Slot Entry' in
            the IDSBK.
          LOCATED BY :
            IDSSTART  contains IDSLTENT entries.

     IDSLTENT DSECT
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    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      IDSLTENT       ISFC ID segment table
    0000    0 Address      4 IDSLTADD       Address of slot entry
                                            0=>available 1=>allocated,
                                            not a pointer
                                            >1=>allocated, pointer to
                                            entry
              00000004       IDSLTBLN       *-IDSLTENT Length of slot entry
                                            in bytes
          IUCV is limited to 64K paths, so each of these tables
          can only have 64K entries.  Each "slot" in a segment
          consists of a fullword, so each segment (4K page) can
          hold 1K slots.  Therefore, the maximum number of segment
          entries per table is 64 and the maximum number of slots
          per segment is 1024.
              00000040       IDSMAXSG       64 Maximum segment entries per
                                            table
              00000400       IDSMAXSL       1024 Maximum slots per segment
              00000001       IDSLTFUL       1 Zero implies slot available
                                            Non-zero implies slot allocated

IDSBK Storage Layout | Top of page

    *** IDSBK - ISFC ID segment table
    *
    *     +---------------------------+---------------------------+
    *   0 |         IDSCOUNT          |         IDSHMARK          |
    *     +---------------------------+---------------------------+
    *   8 |///////////////////////////////////////////////////////|
    *     +-------------------------------------------------------+
    *  10 |                                                       |
    *     =                       IDSSTART                        =
    *     |                                                       |
    *     +-------------------------------------------------------+
    * 210
    *
    *** IDSBK - ISFC ID segment table

    *** IDSEGENT - ISFC ID segment table
    *
    *     +---------------------------+---------------------------+
    *   0 |         IDSEGCNT          |         IDSEGADD          |
    *     +---------------------------+---------------------------+
    *   8
    *
    *** IDSEGENT - ISFC ID segment table

    *** IDSLTENT - ISFC ID segment table
    *
    *     +---------------------------+
    *   0 |         IDSLTADD          | 4
    *     +---------------------------+
    *
    *** IDSLTENT - ISFC ID segment table

IDSBK Cross Reference | Top of page

    Symbol         Dspl Value
    -------------- ---- -----
    IDSCOUNT       0000
    IDSEGADD       0004
    IDSEGBLN       0004 00000008
    IDSEGCNT       0000
    IDSHMARK       0004
    IDSLTADD       0000
    IDSLTBLN       0000 00000004
    IDSLTFUL       0000 00000001
    IDSMAXSG       0000 00000040
    IDSMAXSL       0000 00000400
    IDSSIZE        0010 00000042
    IDSSTART       0010

This information is based on z/VM 7.2.0 Last updated on 24 Jun 2020 at 09:28:34 EDT.
Copyright IBM Corporation, 1990, 2020