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 Top of page
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 Top of page
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 7.3.0 Last updated on 22 Jun 2022 at 15:51:23 EDT.
Copyright IBM Corporation, 1990, 2022