IBM System/360 System Programmer's Guide

The LOCATE macro-instruction points to the CAMLST macro-instruction.
BLOCK, the first operand of CAMLST, specifies that the system is to
search the catalog for the block indicated by TTR, the second operand.
LOCAREA, the fourth operand, specifies a 265-byte area you have reserved
in main storage.
After execut.ion of these macro-instructions, the 265-byte area
contains: the 256-byte index block, the 3-byte relative track address
CTTR) of the block following the one read into main storage, and the
6-byte serial number of the volume on which the block was found.
HOW TO BUILD AN INDEX
To tuild a new index structure and add it to the catalog, you must
create each level of the index separately. You create each level of the
index ty using the INDEX and. CAMLST macro-instructions.
These two macro-instructions can also be used to add index levels to
existing index structures.
Example: In the following example, index structure A.B.C is built on
the control volume whose serial number is 000045.
r---------T----------T-------------------------------------------------,
I Name I Operation I Operand I
t---------f----------f-------------------------------------------------~
INDEX I INDEXA BUILD INDEX A
Check Exceptional Returns
INDEX I INDEXB BUILD INDEX STRUCTURE A.B
Check Exceptional Returns
INDEX I INDEXC BUILD INDEX STRUCTURE A.B.C
Check Exceptional Returns
INDEXA CAMLST I BLDX,ALEVEL,VOINUM
INDEXB CAMLST I BLDX,BLEVEL,VOLNUM
INDEXC CAMLST I BLDX,CIEVEL,VOtNUM
VOLNUM DC I CL6'000045' VOLUME SERIAL NUMBER
ALEVEL DC I CL2'A' INDEX STRUCTURE NAMES
BLEVEL DC I CL4'A.B' FOLLOWED BY BLANKS
CLEVEL DC I CL6'A.B.C' WHICH DELIMIT FIELDS
L- ________ ~ _____ . _____ ~ _________________________________________________ J
Each INDEX macro-instruction points to an associated CAMLST macro-
instruction. BLDX, the first operand of CAMLST, specifies that an index
level be built. The second operand specifies the main storage location
of an area into which you have placed the fully qualified name of an
index level. ThE; third operand specifies the main storage location of
an area into which you have placed the 6-byte serial nuwoer of the
volume on which the index level is to be built.
HOW TO BUILD A GENERATION INDEX
You build a generation index by using the INDEX and CAMLST macro-
instructions. All higher levels of the index must exist. If the higher
levels of the index are not in the catalog, you mus·t build them. How to
build an index has been explained previously. In the following example,
the generation index D is built on the control volurr.e whose serial
number is 000045. The higher level indexes A.B.C already exist. When
the number of generation data sets in the generation index D exceeds
four, the oldest data set in the group is uncataloged and scratched.
Maintaining the Catalog and the Volurre Table of contents 13

IBM System/360 Specifications

General

Brand	IBM
Model	System/360
Category	Desktop
Language	English