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.

HASHTAB

Prolog  

Control Block Contents  

HASHTAB DSECT

Storage Layout  

Cross Reference (Contains links to field and bit definitions)  

HASHTAB Prolog

Name : HASHTAB Description: Hash Table Complex DSECT : HASHTAB Function : HASHTAB is used exclusively by file management to reduce the paging overhead when searching for a file on a read/write disk. It contains a header plus a pointer array with the address of each hyperblock associated with the disk, and a scatter index table with a 4-byte entry for each file on the disk. HASHTAB is called by the HASHTAB macro.

 

HASHTAB Control Block Content


HASHTAB DSECT

Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure HASHTAB Hash Table Complex H E A D E R 0000 0 Signed 4 HYPTSIZE Size of Hyperblock Address Table (bytes) 0004 4 Signed 4 SCTSIZE Size of Scatter Table (bytes) 0008 8 Signed 4 NSCTSLOT Number of 4 byte slots in Scatter Table 000C 12 Signed 4 NSCTUSED Number of used Scatter Table slots 0010 16 Character 7 HASHEYEC Hash Table eyecatcher 0017 23 Character 1 HASHVERS Hash Table version number 0018 24 Character 8 * Reserved 00000020 HSHLENHD *-HASHTAB Size of header H Y P E R B L O C K A D D R E S S T A B L E 0020 32 Signed 4 HYPTABLE (0) Start of Hyperblock Address Portion 0020 32 Signed 4 HYPADD Address of hyperblock 00000004 HADDLEN *-HYPADD Size of an address entry S C A T T E R T A B L E 0024 36 Signed 4 SCATTRTB (0) Start of Scatter Table Portion 0024 36 Signed 3 HTABINDX Index into hyperblock address table 0027 39 Character 1 SECHBYTE Secondary hash byte 00000004 SLOTSIZE *-HTABINDX Size of a Scatter Table slot

 

HASHTAB Storage Layout

*** HASHTAB - Hash Table Complex
*
*     +---------------------------+---------------------------+
*   0 |         HYPTSIZE          |         SCTSIZE           |
*     +---------------------------+---------------------------+
*   8 |         NSCTSLOT          |         NSCTUSED          |
*     +---------------------------+--------------------+------+
*  10 |                   HASHEYEC                     |:HVERS|
*     +------------------------------------------------+------+
*  18 |///////////////////////////////////////////////////////|
*     +---------------------------+--------------------+------+
*  20 |          HYPADD           |     HTABINDX       |:HBYTE|
*     +---------------------------+--------------------+------+
*  28
*
*** HASHTAB - Hash Table Complex

 

HASHTAB Cross Reference

(contains links to field and bit definitions)
Symbol         Dspl Value
-------------- ---- -----

HADDLEN 0020 00000004

HASHEYEC 0010

HASHVERS 0017

HSHLENHD 0018 00000020

HTABINDX 0024

HYPADD 0020

HYPTABLE 0020

HYPTSIZE 0000

NSCTSLOT 0008

NSCTUSED 000C

SCATTRTB 0024

SCTSIZE 0004

SECHBYTE 0027

SLOTSIZE 0027 00000004


This information is based on VM/ESA 2.4.0.
Last updated on 12 Aug 1999 at 11:21:23 EDT.
Copyright IBM Corporation, 1990, 1999