IBM System/360 User guide

Systems Reference Library
IBM System/360 Operating System
System Programmer's
Guide
This publication describes:
File No. S360-20
Form C28- 6550- 2 OS
• How to maintain the data set cataloging facility of
the Operating System and the volume-table-of-
contents (VTOC) of a direct-access volume.
• How to modify or extend capabilities of the Operat-
ing System in the areas of job and job-step
accounting~ processing of magnetic tape labels, and
SVC routines.
• How to implement the data set protection feature of
the Operating System.
• How to write a shift initiator program for use when
the multiprogramming with a fixed number of tasks
(MFT) option is incorporated in the Operating
System.
• How to use the EXCP (Execute a Channel Program) and
XDAP (Execute a Direct-Access Program) macro-
instructions, the Resident Access-Method and BLDL
Table options, and the tracing routine.
Also included are descriptions of system macro-
instructions used in modifying the control program.

PREFACE
This publication consists of self-
contained chapters, each of which provides
information on how to modify or extend the
capabilities of the IBM System/360
Operating System control program. Although
the information in one chapter is sometimes
related to information in another, all
chapters have been written as separate and
complete units. Each chapter contains its
own introductory section and list of pre-
requisite publications. This organization
has been used to reduce cross-referencing
and to facilitate the addition of new
chapters.
Third Edition (March 1967)
This publication is a revision of Forms C28-6550-0 and C28-6550-1 and
obsoletes the previous editions. This publication retains the content
of the previous editions, as amended by Technical Newsletters N28-2145,
N28-2157, N28-2162, N28-2183, N28-2188, and N28-2207, with the following
exceptions:
The format and field description of the Data Set Control Blocks, the
Data Extent Block, and the Job File Control Block are dele-ted.
The chapter Cataloged Procedures is deleted.
Additions and changes to existing material that are effective as of
this edition, are indicated by a vertical bar in the left margin.
Specifications contained
time. Any such change will
Technical Newsletters.
herein are subject to change from time to
be reported in subsequent revisions or
This publication was prepared for production using an IBM computer to
update the text and to control the page and line format. Page
impressions for photo-offset printing were obtained from an IBM 1403
Printer using a special print chain.
copies of this and other IBM publications can be obtained through IBM
Branch Offices.
A form for readers' conunents appears at the back of this publication.
It may be mailed directly to IBM. Address any additional conunents
concerning this publication to the IBM Corporation, Progranuning Systems
Publications, Department D58, PO Box 390, Poughkeepsie, N. Y. 12602
~ International Business Machines corporation 1966, 1967

CONTENTS
MAINTAINING THE CATALOG AND THE VOLUME TABLE OF CONTENTS. 9
Maintaining the Catalog and the Volume Table of contents.
How to Read a Block From the Catalog • • • • • •
Specifying the Name of an Index Level or Data Set •
Specifying the Name of a Generation Data Set ••
Specifying a Name Using an Alias. •
Specifying by TTR • • • • • •
How to Build an Index. • • • • •
How to Build a Generation Index.
How to Delete an Index • •
How to Assign an Alias • • • • •
How to Delete an Alias • • • • .
How to Connect Control Volumes •
How to Disconnect Control Volumes.
How to Catalog a Data Set. • • • • •
How to Remove Data Set References From the Catalog •
How to Recatalog a Data Set ••
• • 10
• 10
• . •• 10
• • • 11
· • . 12
• • • 12
• 13
• 13
• . 14
• . 14
• . 15
• • • • • . 15
• 16
• 17
• • • 17
· 18
How to Read a Data Set Control Block From the Volume Table of
Contents. • • • • •
How to Delete a Data Set
How to Rename a Data Set
Appendix A: Catalog Block Entries.
Control Entries • • • • • • •
Pointer Entries • • • • • • •
The Volume Control Block Contents • • •
Appendix B: Device Code Designations ~
ADDING SVC ROUTINES TO THE CONTROL PROGRAM.
Writing SVC Routines. • • • . • • • • .
Characteristics of SVC Routines • • • • . •
Programming conventions for SVc'Routines.
• • • 18
· 19
• • • • • • 20
• • • • • • • • • • 25
• 25
• • • • • • • 26
• • • • 28
• 29
• • • 31
• • 32
32
• • 32
Inserting SVC Routines Into the Control Progra_ • . • • • • • 37
Specifying SVC Routines ••• • • • • . • • • . . 37
Inserting SVC Routines During the System Generation Process • • 37
ADDING AN ACCOUNTING ROUTINE TO THE CONTROL PROGRAM. • •• 39
Writing an Accounting Routine • •
40
Inserting an Accounting Routine Into the Control Program. • • . 41
Inserting an Accounting Routine Before System Generation.. 41
Inserting an Accounting Routine After System Generation • • • • 41
NONSTANDARD LABEL PROCESSING ROUTINES; VOLUME
DUAL-DENSITY TAPE DEVICE EDITOR ROUTINES •.
LABEL
AND
Section 1: Writing Nonstandard Label
Input Header Label Routines •
Input Trailer Label Routine •
Output Header Label Routines.
Output Trailer Label Routines
programming Conventions • • •
Program Functions . • • • • •
Explanations of Logic Blocks.
Processing Routines • •
Inserting Nonstandard Label Routines Into the Control Program •
• 43
• 44
44
• • 44
44
• • 45
45
46
• 52
• 53

Section 2:
Volume Label and Dual-Density Tape Device Editor
Routines • • •
55
Programming Conventions
• • • • 55
Entry Conditions and General Logic Flow of the Editor Routines. • • • 56
Entry Conditions • • • • • • • • • • • • . • • 56
General Logic Flow • • • • • • • • 58
Logic Block Explanations. • • • •
61
Inserting Your Label Editor Routines Into the Control Program • . • . 63
Appendix: IECDSECT,IEFJFCBN, and IEFUCBOB Macro-Instructions • · • •
65
IECDSECT Macro-Instruction • • • • • • • . • • • •
Control Statements Required • • • • •
IECDSECT
Macro-Definition • • • • • .
IEFUCBOB Macro-Instruction • . • • • • •
Control Statements Required • • . • .
IEFUCBOB Macro-Definition • • •• • . • • . • •
IEFJFCBN Macro-Instruction . . • . . • •
Control statements Required • . • • • • •
IEFJFCBN Macro-Definition • . • • • •
EXECUTE CHANNEL PROGRAM (EXCP) MACRO-INSTRUCTION.
Execute Channel Program (EXCP) Macro-Instruction.
Use of EXCP in System and Problem Programs. •
System Use of EXCP • • •
Programmer Use of EXCP
EXCP Requirements • • • • • •
Channel Program. • • • • . • • •
Data and Command Chaining
Control Blocks • . • • • • •
Input/Output Block (lOB).
Event Control Block (ECB)
Data Control Block (DCB) ••.
Data Extent Block (DEB)
· • . 65
· 65
· . • • • . 65
• 70
• • • 70
• • 70
· • • 71
• 72
• • • • • • 72
• • 74
• 75
• • • 75
75
• • • • • • 76
• 76
76
• • 76
• • • 77
• 77
• • 77
· 77
• 77
Channel Program Execution • . • • • • • •
78
Initiation of Channel Program. •
Completion of Channel Program. • • • • • • •
78
• • • • • • • 79
• • • • • • 79
Device End Errors . • • • . •
Interruption Handling and Error Recovery
Error Recovery Procedures for Related
Procedures. •
Channel Programs.
• • • • 79
• • 79
Appendages. • • • •••••
Defining Appendages. • •
Entering Appendages Into SVC Library •
Characteristics of Appendages ••.•
Start Input/Output (SIO) Appendage.
Program Controlled Interruption (PCI)
End-of-Extent Appendage
Channel End Appendage • •
Abnormal End Appendage. •
EXCP Programming Specifications
Macro-Instructions • • • . •
Appendage
DCB -- Define Data Control Block for EXCP .
OPEN -- Initialize Data Control Block .
EXCP -- Execute Channel Program . •
EOV -- End of Volume. • • • • ~. • • • . • • • • • •
CLOSE -- Restore Data Control Block • .
Control Block Fields . • • • . •
Input/Output Block Fields . •
Event Control Block Fields ••
• • • 80
• • 80
• • • • 80
· 81
• • • • 82
• • • • • • 82
• 82
· 83
• 83
• • 84
• 84
• • • 84
• • • • • • 90
• • . 91
• • • • 91
• • • 92
• 93
• 93
• • 95

Data Extent Block Flelds •.•.•
Appendix: Restore Macro-Instruction .•.
RESTORE Macro-Instruction • •
Control Statements Required •
RESTORE Macro-Definition •••
. '. . . · .
96
• 97
97
97
• 97
EXECUTE DIRECT ACCESS PROGRAM (XDAP) MACRO-INSTRUCTION. . • • . 98
Execute Direct Access Program (XDAP) Macro-Instruction. . • •
99
Requirements for Execution of Direct-Access Program
• • 99
XDAP Programming Specifications . • . • . . • •
.100
• .100
Macro-Instructions • • • . • . . . • • . •
DCB -- Define Data Control Block. . . •
OPEN -- Initialize Data Control Block .
XDAP -- Execute Direct-Access Program •
EOV -- End of Volume. . • • •
d • • • • .100
.. • • • • . • • • .100
. • • • . • .100
.101
CLOSE -- Restore Data Control Block
• .101
The XDAP Control Block • • •
Event Control Block (ECB) • •
Input/Output Block (lOB) •••
Direct-Access Channel Program
. • • • • . • . • .102
XDAP Options •••.••••••••
· •. 102
• •. 103
.103
.103
Conversion of Relative Track Address to Actual Address . ·
.103
Appendages • • • • • • • • • • . • • • • • .
L- and E- Forms of XDAP Macro-Instruction.
Appendix: CVT Macro-Instruction. . • • .
HOW
Format of the CVT Macro-Instruction
Control Statements Required •
CVT Macro-Definition. • • • •
TO
USE THE TRACING ROUTINE
HOW TO USE THE TRACING ROUTINE
Table Entry Formats • _
Location of the Table • • . •
IMPLEMENTING DATA SET PROTECTION
Implementing Data Set Protection .•
Password Data Set Characteristics and Record Format •
Protecting the Password Data Set ••
Creating Protected Data Sets .•••
Protection Feature Operating Characteristics.
Termination of Processing . • . • • • •
Volume Switching. . • • •••
Data Set Concatention • • • •
SCRATCH and RENAME Functions.
Counter Maintenance • • • • .
• •. 104
.104
• .105
.105
• ••. 105
• •. 105
• .108
• •. 109
· •. 109
· •. 109
• .111
• ••• 112
• .112
• .113
.113
· .•. 113
· .•. 113
· • • . . .114
· •. 114
.114
· . • • . .114
THE RESIDENT BLDL TABLE AND RESIDENT ACCESS 'METHOD OPTIONS •. 115
The Resident BLDL Table and Resident Access Method Options •.
· .116
The Resident BLDL Table Option. • . •
Selecting Entries for the Resident BLDL Table. . . • •
Table Size. • • . • • • • •
Frequency of Use. • • • . . •
The Resident Access Method Option •
•
•. 116
.117
· . • . • .117
• ••••. 117
.117

Considerations for Use • • • • •
Creating Procedure Library Lists ••
Example. • • • • • • • • • • • •
•
.117
.118
.118
Appendix A: Resident Access Method Option - Standard List IEAIGGOO .120
CONSTRUCTING A DUMMY WAITR ROUTINE.
Constructing a Dummy WAITR Routine. •
Functions of the Dummy WAITR Routine. •
A Coding Example • • • • • •
Job Control Language Statements
Programming Considerations.
SYSTEM MACRO-INSTRUCTIONS ••
Locate Device Characteristics (DEVTYPE) Macro-Instruction
Device Characteristics Information. • • • • • •
Output for Each Device Type • • • • • • • •
Exceptional Returns • • • • • • • •
.121
• .122
.122
•••• 122
•••• 123
• .124
.125
• .126
• .126
• • .128
.129
How to Read a Job File Control Block. • • • • • • • .130
OPEN -- Prepare the Data Control Block for Processing (S> ••. 130
RDJFCB -- Read a Job File Control Block (S> . • • • • • .131

ILLUSTRATIONS
FIGURES
Figure 1. Status of Control Information and Pointers •••••••• 47
Figure 2. Format of Combined Work and Control Block Area •••••• 48
Figure 3. General Flow of a Nonstandard Label Processing Routine
After Receiving Control From the OPEN Routine. • • • • . • • • • • • 49
Figure 4. General Flow of a Nonstandard Label Processing Routine
After Receiving Control FrOID the CLOSE Routine • • • • • • • • . • . 50
Figure 5 • GenE~ral Flow of a Nonstandard Label Processing Routine
After Receiving Control Frorr the EOV Routine • • • • • • • • • • 51
Figure 6. Editor Routine Entry Conditions. . • . . .• • 57
Figure 7. General Flow of an Editor Routine After Receiving
Control From the OPEN Routine. • • • • • • • • • • • • • • 59
Figure 8. General Flow of an Editor Routine After Receiving
Control From the End-of-Volume Routine • • • . • • • 60
Figure 9. Data Control Block Format for EXCP (After OPEN). •• 86
Figure 10. Input/Output Block Format. • • • • • . • • .. • •• 93
Figure 11. Event Control Block After Posting of Completion Code. 95
Figure 12. Event Control Block After Posting of Completion Code ••• 102
Figure 13. The XDAP Channel Programs. • • • • • • • • . • • .103
TABLES
Table 1. Programming Conventions for SVC Routines •••••••.•• 33

MAINTAINING THE CATALOG AND THE VOLUME TABLE OF CONTENTS
This chapter provides detailed informa-
tion on how to maintain and modify the
catalog and volume table of contents.
Before reading this chapter, you should
be familiar with the information contained
in the prerequisite publications listed
below.
Documentation of the internal logic of
the routines used to maintain and modify
the catalog and volume table of contents
can be obtained through your IBM Branch
Office.
PREREQUISITE PUBLICATIONS
The IBM System/360 operating System:
Assembler Language publication (Form
C28-6514) contains the information neces-
sary to code programs in the assemtler
language.
The IBM System/360 operating Systerr:
Data ~anagement publication (Form C28-6537)
contains a general description of the
structure of catalog indexes, as well as a
brief discussion of the volume tatle of
contents (V'roc).
The IBM System/360 Operating System:
Control Program Services publication (Form
C28-6541) contains an explanation of" the
notation conventions used to describe the
macro-instructions contained in this chap-
ter.
The IBM System/360 Operating System:
System Control Blocks publication (Form
C28-6628) contains format and field de-
scriptions of the system control tlocks
referred to in this chapter.
RECOMMENDED PUBLICATIONS
The IBM System/360 Operating System:
utilities publication (Form C28-6586) de-
scribes how to maintain and ITodify the
catalog and the volume table of contents
through the use of utility programs.
Maintaining the Catalog and the Volume Table of contents 9

MAINTAINING THE CATALOG AND THE VOLUME TABLE OF CONTENTS
This chapter describes how to maintain and modify the catalog and the
volume table of contents through the use of macro-instructions. Most of
the maintenance and modification functions can also be performed using
utility statements. The utility statements are described in the
publication IBM System/360 Operating System: Utilities.
The functions you can perform using the macro-instructions are
described in text, and the formats of the macro-instructions are
tabulated on a fold-out sheet at the tack of this chapter. The chart on
the fold-out sheet associates the function described in text with the
macro-instructions needed to perform the function. You should keep the
fold-out sheet open when reading the text.
The functions that are described in text are as follows:
•
How to
read a block fron: the catalog.
•
How to build
an
index.
•
How to
build
a
generation index.
•
How
to delete an
index.
•
How to assign
an
alias.
•
How to
delete an alias.
•
How to
connect control
volumes.
•
How
to
disconnect control volumes.
•
How to catalog a data set.
•
How to rerr,ove
data set
references from the catalog.
•
How
to recatalog
a
data set.
•
How to
read a data
set control block from the volume table of
contents.
• How to delete a data set.
• How to rename a data set.
Accompanying the function descriptions in text are coding examples
and programm1ng notes; exceptional-return condition codes for the
macro-instructions are tabulated on the back of the fold-out sheet.
HOW TO READ A BLOCK FROM THB CATALOG
To read either an index block or a block indicating the volumes on
Which a data set is stored (volume-list block), you use the LOCATE and
CAMLST macro-instructions. There are two ways to specify the block that
you want read into main storage: by using the nawe of the index level or
data set, or by using the block's location relative to the beginning of
the catalog (TTR).
Specifying the Name of an Index Level or Data Set
If you specify an index level name, the first block of the named
index is read int,o main storage, and an exceptional return code is set.
Index tlock formats are contained in Appendix A of this chapter.
If you specify a data set name, a 256-byte volume-list block is read
into main storage. The block contains up to 20 volume pointers, each of
which points to a volume on which ~art of the data set is stored. The
first two bytes of the block contain the number of volume pointers for
the data set. Each volume pointer is a 12-byte field that contains a
4-byte device code, a 6-byte volume serial number, and a 2-byte data set
sequence number. (Device codes are contained in Appendix B of this
chapter.)
10

If the nam4ed data set is stored on more than 20 vol urnes, bytes
253-255 of the block contain the relative track address of the next
block of volume pointers. Byte 256 contains a binary zero.
Example: In the following example, the list of volumes that contain
data set A.B is read into main storage. The search for the volume-list
block starts on the system residence volume.
r---------T----------T-------------------------------------------------,
I Name I Operation I Operand ~
~---------+----------+-------------------------------------------------i
I I LOCATE I INDAB READ VOLUME-LIST BLOCK FOR I
I I Check Exceptional Returns CATALOGED DATA SET A.B INTOI
I
INDAB I CAMLST I NAME,AB"LOCAREA MAIN STORAGE AREA NAMED I
I
AB I DC I CL44'A.B' LOCAREA. LOCAREA ALSO I
I LOCAREA I DS I OD CONTAINS 3-BYTE TTR AND I
I I
DS I 265C 6-BYTE SERIAL NUMBER I
L _________ ~ ___________ ~ _________________________________________________ J
The LOCATE macro-instruction points to the CAMLST macro-instruction.
NAME, the first operand of CAMLST, specifies that the system is to
search the catalog for a volume-list tlock by using the name of a data
set. AB, the second operand, specifies the main storage location of a
44-byte area into which you have placed the fully qualified name of a
data set. LOCAREA, the fourth operand, specifies a 265-byte area you
have reserved in main storage.
After execution of these macro-instructions, the 265-byte area
contains: the 256-byte volurre-list block for data set A.B, the 3-byte
relative track address (TTR) 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 ..
Specifying the Name of a Generation Data Set
You specify the name of a generation data set by using the fully
qualified generation index name and the relative generation number of
the data set. The value of a relative generation number reflects the
position of a data set in a generation data group. The following values
can be used:
• Zero - specifies the latest data set cataloged in a generation data
group.
• Negative nt~ber - specifies a data set cataloged before the latest
data set.
• Positive number - specifies a data set not yet cataloged in the
generation data group.
When you use zero or a negative number as the relative generation
number, a volume-list block is read into main storage and the relative
generation number is replaced by the absolute generation name.
When you USE~ a positive number as the relative generation number, an
absolute generation name is created and replaces the relative generation
number. A volume-list block is not read, since none exists for these
data sets.
Example: In t.he following example, the list of volumes that contain
generation data set A.PAY(-3) is read into main storage. The search for
the volume-list block starts on the system residence volume.
Maintaining the Catalog and the Volume Table of contents 11

r---------T----------T-------------------------------------------------,
I Name I operationl Operand I
~---------+----------+-------------------------------------------------~
I I LOCATE I INDGX READ VOLUME-LIST BLOCK FOR I
I I
Check Exceptional Returns DATA SET A.PAY(-3) INTO I
I INDGX I CAMLST I NAME,APAY"LOCAREA MAIN STORAGE AREA NAMED I
I APAY I DC I CL44'A.PAY(-3)' LOCAREA. LOCAREA ALSO CON- i
I LOCAREA I DS I OD TAINS 3-BYTE TTR AND I
I I DS I 265C 6-BYTE SERIAL NUMBER I
L _________ ~-- ________ ~ _________________________________________________ J
The LOCATE macro-instruction points to the CAMLST macro-instruction~
NAME, the first operand of CAMLST, specifies that the system is to
search the catalog for a volume-list block by using the name of a data
set. APAY, the second operand, specifies the main storage location of a
44-byte area into which you have placed the name of the generation index
and the relative generation number of a data set in the generation data
group. LOCAREA, the fourth operand, specifies a 265-byte area you have
reserved in main storage.
After execution of these macro-instructions, the 265-byte area
contains: the 256-byte volurre-list clock for generation data set
A. PAY(-3), the 3-byte relative track address ('ITR) of the block
following the one read into rrain storage, and the 6-byte serial number
of the volume on which the block was found. In addition, the system
will have replaced the relative generation number that. you specified in
your 44-byte area with the data sst's absolute generation name.
§pecifying a Name Using an Alias
For each of the preceding functions, you can specify an alias as the
first name in the qualified name of an index level, data set, or
generation data set. Each function is performed exactly as previously
described, with one exception: the alias narre specified is replaced by
·the true name.
§pecifying by TTR
You
can read any block in the catalog by specifying, in the form TTR,
the identification of the block and its location relative to the
beginning of the catalog. TT is the number of tracks defining the
position, relative to the beginning of the catalog, of the track on
which the block to be read resides; R is the identification of the block
on that track. (Formats of each type of catalog block are contained in
Appendix A of this chapter.)
Example: In the following example, the block at the location indicated
by TTR is read into main storage. The specified block is in the catalog
on the system residence volume.
r---------T----------T-------------------------------------------------,
I Name I Operationl Operand I
t---------+----------+-------------------------------------------------~
I I LOCATE I BLK READ A BLOCK INTO MAIN I
I I
Check Exceptional Returns STORAGE AREA NAMED LOCAREA I
I
BLK I CAMLST I BLOCK,TTR"LOCAREA I
I 'ITR I DC I H' 5' RELATIVE TRACK 5 I
I I DC I X'03' BLOCK 3 ON TRACK I
I LOCAREA I DS I 00 LOCAREA ALSO CONTAINS 3-BYTEI
I I DS I 265C TTR AND 6-BYTE SERIAL NO. I
L _________ ~ __________ ~ _________________________________________________ J
12

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

r---------T----------T-------------------------------------------------,
I Name I operation I Operand I
~---------+----------+-------------------------------------------------~
I I INDEX I GENINDX BUILD GENERATION I
I I Check Exceptional Returns INDEX I
I GENINDX I CAMLST I BLDG,DLEVEL,VOLNUM"DELETE,,4 I
I DLEVEL I DC I CLsrA.B.C.D' BLANK DELIMITER I
I
VOLNUM I DC I CL6'000045' I
L _________ ~ __________ ~ _________________________________________________ J
The INDEX macro-instruction points to the CAMLST macro-instruction.
BLDG, the first operand of CAMLST, specifies that a generation index be
built. DLEVEL, the second operand, specifies the main storage location
of an area into which you have placed the fully qualified name of a
generation index. VOLNUM, the third operand, specifies the main storage
location of an area into which you have placed the 6-byte serial number
of the volume on which the generation index is to be built. DELETE, the
fifth operand, specifies that all data sets dropped from the generation
data group are to be deleted. The final operand, 4, specifies the
number of data sets that are to be maintained in the generation data
group.
Note: A model DSCB for the generation data set must be placed on the
control volume containing the index prior to creation of the data set.
The system will take information from the model DSCB when you create a
data set for the group. A model DSCB is created by specifying, in a DD
statement: the name of the data set; zero space allocation, i.e.,
SPACE=(TRK, (0»; and appropriate DCB=parameters.
HOW TO DELETE AN INDEX
You can delete any number of index levels from an existing index
structure. Each level of the index is deleted separately. You delete
each level of the index by using the INDEX and CAMLST macro-
instructions.
If an index level either has an alias, or has other index levels or
data sets cataloged under it, it cannot be deleted.
Example: In the following example, index level C is deleted from index
structure A.B.C. The search for the index level starts on the system
residence volume.
r---------T----------T-------------------------------------------------,
I Name I Operation I Operand I
~---------+----------+-------------------------------------------------~
I I INDEX I DELETL DELETE INDEX LEVEL C FROM I
I I
Check Exceptional Returns INDEX STRUCTURE A.B.C I
I DELETE I CAMLST I DLTX,LEVELC I
I
LEVELC I DC I CL6'A.B.C' ONE BLANK FOR DELIMITER I
L _________ ~ __________ ~ _________________________________________________ J
The INDEX macro-instruction points to the CAMLST macro-instruction.
DLTX, the first operand of CAMLST, specifies that an index level be
deleted. LEVELC, the second operand, specifies the main storage
location of an area into which you have placed the fully qualified name
of the index structure whose lowest level is to be deleted.
HOW TO ASSIGN AN ALIAS
You assign an alias to an index level by using the INDEX and CAMLST
macro-instructions. An alias can be ass~gnea only to a high level
index; e.g., index A of index structure A.B.C can have an alias, but
14

index B cannot. Assigning an alias to a high level index effectively
provides aliases for all data sets cataloged under that index.
Example:
of x.
volume.
In the following example, index level A is assigned an alias
The search for the index level starts on the system residence
r---------T----------T-------------------------------------------------,
I Name I Operation I Operand I
~---------+-----.-----+-------------------------------------------------i
I I INDEX I ALIAS BUILD AN ALIAS FOR A HIGHI
I I Check Exceptional Returns LEVEL INDEX I
I ALIAS I
CAMLST I BLDA,DSNAME"DSALIAS I
I
DSNAME I DC I CL8'A' MUST BE 8-BYTE FIELDS I
I DSALIAS I DC I CL8'X' I
L _________ i __________ i _________________________________________________ J
The INDEX macro-instruction points to the CAMLST macro-instruction.
BLDA, the first operand of CAMLST, specifies that an alias be built.
DSNAME, the second operand, specifies the main storage location of an
8-byte area into which you have placed the name of the high level index
to be assigned an alias. DSALIAS, the fourth operand, specifies the
main storage location of an 8-byte area into which you have placed the
alias to be assigned.
HOW TO DELETE AN ALIAS
You delete an alias previously assigned to a high level index ty
using the INDEX and CAMLST macro-instructions.
Example: In the following example, alias X, previously assigned as an
alias for index level A, is deleted. The search for the alias starts on
the system residence volume.
r---------T----------T-------------------------------------------------,
I Name I Operation I Operand I
~---------+----------+-------------------------------------------------i
I I INDEX I DELALIAS DELETE AN ALIAS FOR A I
I I Check Exceptional Returns HIGH LEVEL INDEX I
I DELALIASI CAMLST I DLTA,ALIAS I
I ALIAS I
DC I CL8'X' MUST BE 8-BYTE FIELD I
L _________ i ______ . ____ i ________ --- ______________________________________ J
The INDEX macro-instruction points to the CAMLST macro-instruction.
DLTA, the first operand of CAMLST, specifies that an alias be deleted.
ALIAS, the second operand, specifies the main storage location of an
8-byte area into which you have placed the alias to be deleted.
HOW TO CONNECT CONTROL VOLUMES
You connect two control volumes by using the INDEX and CAMLST
macro-instructions. If a control velume is to be connected to the
system residence volume, you need supply only the serial nurober of the
volume to be connected and the nawe of a high level index associated
with the volume to be connected.
If a control volume is to be connected to a control volume other than
the system residence volume, you must supply the serial numbers of both
volumes and the name of a high level index associated with the volume to
be connected.
The result of connecting control volumes is that the volume serial
number of the control volUme connected and the name of a high level
Maintaining the Catalog and the Volume Table of Contents 15

index are entered into the volume index of the volume to which it was
connected. This entry is called a control volume pointer. A control
volume pointed to by a control volun;e cannot, in turn, point to another
control volume.
Example: In the following example, the contrel voluroe whose serial
number is 001555 is connected to the control volume numbered 000155.
The name of the high level index is HIGHINDX.
r---------T----------T-------------------------------------------------,
I Name I Operation I Operand I
~---------+----------+-------------------------------------------------~
I I INDEX I CONNECT CONNECT TWO CON- I
I I
Check Exceptional Returns TROL VOLUMES WHOSE I
I CONNECT I CAMLST I LNKX,INDXNAME,OLDCVCL,NEWCVOL SERIAL NUMBERS AREI
I INDXNAMEI DC I CL8'HIGHINDX' 000155 AND 001555. I
I OLDCVOL I DC I CL6'000155' I
I NEWCVOL I DC I CL6'001555' I
L _________ ~ __________ ~ _________________________________________________ J
The INDEX rracro-instruction points to the CAMLST macro-instruction.
LNKX, the first operand of CAMLST, specifies that control volumES be
connected. INDXNAME, the second operand, specifies the main storage
location of an 8-byte area into which you have placed the name of the
high level index of the volume to be connected. OLDCVOL, the third
operand, specifies the main storage location of a 6-byte area into which
you have placed the serial number of the volume to which you are
connecting. NEWCVOL, the fcurth operand, specifies the main storage
location of a 6-byte area into which you have placed the serial number
of the volume to be connected.
HOW TO DISCONNECT CONTROL VOLUMES
You disconnect two control volumes by using the INDEX and CAMLST
macro-instructions. If a control vclume is to be disconnected from the
system residence volume, you need supply only the name of the high level
index associated with the volurre to be disconnected.
If a control volume is to be disconnected from a control volume other
than the system residence volume, you must supply, in addition to the
name of the high level index, the serial nurr-ber of the control volume
from which you want to disconnect.
The result of disconnEcting control volumes is that the control
volume pointer is removed from the volume index of the volume from which
you are disconnecting.
Example: In the following example, the control volume that contains the
high level index HIGHINDX is disconnected from the system residence
volume.
r---------T----------T---------------------'----------------------------,
I Name I Operationl Operand I
~---------+----------+------------------,-------------------------------~
I I INDEX I DISCNECT DISCONNECT TWO CONTROL I
I I
Check Exceptional Returns VOLUMES I
I DISCNECTI
CAMLST I DRPX,INDXNAME I
I INDXNru~EI DC I CL8'HIGHINDX' MUST BE 8-BYTE FIELD I
L _________ L __________ L _________________________________________________ J
The INDEX macro-instruction points to the CAMLST macro-instruction.
DRPX, the first operand of CAMLST, specifies that control volumes be
disconnected. INDEXNAME, the second operand, specifies the main storage
16

location of an 8-byte area into which you have placed the name of the
high level index of the control volume to be disconnected.
HOW TO CATALOG A DATA SEr
You catalog a data set by using the CATALOG and CAMLST macro-
instructions. All inde* leve~s required to catalog the data set must
exist in the catalog, or an exceptional return code is set.
You must build a complete volume list in main storage. This volume
list consists of volume pointers for all volurres on which the data set
is stored. The first two bytes of the list indicate the number of
volume pointers that follow. Each 12-byte volume pointer consists of a
4-byte device code, a 6-byte volume serial number, and a 2-byte data set
sequence number. The sequence number is always zero for 'direct-access
volumes. (Device codes are contained in Appendix B of this chapter.)
Example: In the following example, the data set named A.B.C is
cataloged under an existing index structure A.B. The data set is stored
on two volumes.
r---------T----------T---------~---------------------------------------,
I Name I Operation I Operand I
~---------+----------+-------------------------------------------------~
I I CATA:LOG I ADDABC CATALOG DATA SET A.B.C. THE I
, I
Check Exceptional Returns INDEX STRUCTURE A.B. EXISTS I
I
ADDABC I CAMLST I CAT,DSNAME"VOLUMES I
I
DSNAME I DC , CL6'A.B.C' ONE BLANK FOR DELIMITER I
I
VOLUMES I DC I H ,. 2' TWO VOLUMES I
I ,
DC , X'30002001' 2311 DISK STORAGE I
, , DC , CL6'000014' VOLU~E SERIAL NUMBER ,
, I DC , H' 0' DATA SET SEQUENCE NUMBER I
, I DC I X'30002001' 2311 DISK STORAGE I
, , DC I CL6'000015' VOLUME SERIAL NUMBER I
, , DC , H'O' SEQUENCE NUMBER ,
L _________ ~ __________ ~ _________________________________________________ J
The CATALOG macro-instruction points to the CAMLST macro-instruction.
CAT, the first operand of CAMLST, specifies that a data set be
cataloged. DSNAME, the second operand, specifies the main storage
location of an area into which you have placed the fully qualified name
of the data set to be cataloged. VOLUMES, the fourth operand, specifies
the main storage location of the volume list you have built.
HOW TO REMOVE DATA SET REFERENCES FROM THE CATALOG
You remove data set references from the catalog by using the CATALOG
and CAMLST macro-instructions.
Example: In the following example, references to data set A.B.C are
removed from the catalog.
r---------T-----------T-------------------------------------------------,
'Name I Operation, Operand I
~---------+----------+-------------------------------------------------~
I I CATALOG I REMOVE REMOVE REFERENCES TO DATA I
I I
Check Exceptional Returns SET A.B.C FROM THE CATALOG I
I REMOVE I CAMLST I UNCAT,DSNAME I
I
DSNAME I DC I CL6'A.B.C' ONE BLANK FOR DELIMITER I
L _________ ~ ___________ ~ _________________________________________________ J
The CATALOG macro-instruction points to the CAMLST macro-instruction.
UNCAT, the firs·t cperand of CAMLST, specifies that references to a data
Maintaining the Catalog and the Volurre Table of Contents 17

set be removed from the catalog. DSNAME, the second operand, specifies
the main storage location of an area into which you have placed the
fully qualified name of the data set whose references are to be removed.
HOW TO RECATALOG A DATA SET
You recatalog a cataloged data set by using the CATALOG and CAMLST
macro-instructions. Recataloging is usually performed when new volume
pointers must be added to the volume list of a data set.
You must build a complete volume list in main storage. This volurre
list consists of volume pointers for all volumes on which the data set
is stored. The first two bytes of the list indicate the number of
volume pointers that follow. Each 12-byte volume pointer consists of a
4-byte device code, a 6-byte volume serial number, and a 2-byte data set
sequence number. The sequence number is always zero for direct-access
volumes. (Device codes are contained in Appendix B of this chapter.)
Example: In the following example, the data
recataloged. A new volume pointer is added to the
previously contained only two volume pointers.
set named A.B.C is
volume list, which
r---------T----------T-------------------------------------------------,
I Name I Operationl Operand I
~---------+----------+-------------------------------------------------~
RECATLG
DSNAME
VOLUMES
CATALOG I RECATLG RECATALOG DATA SET A.B.C,
Check Exceptional Returns ADDING A NEW VOLUME
POINTER TO THE VOLUME
CAMLST RECAT,DSNAME"VOIUMES LIST.
DC CL6'A.B.C' ONE BLANK FOR DELIMITER
DC H' 3' THREE VOLUMES
DC X'30002001' 2311 DISK STORAGE
DC CL6'000014' VOLUME SERIAL NUMBER
DC H' 0' SEQUENCE NUMBER
DC X'30002001' 2311 DISK STORAGE
DC CL6'OOOOlS' VOLUME SERIAL NUMBER
DC H'O' SEQUENCE NUMBER
DC X'30002001' 2311 DISK STORAGE
DC CL6'000016' VOLUME SERIAL NUMBER
DC H'O' SEQUENCE NUMBER
---------~----------~-------------------------------------------------
The CATALOG macro-instruction points to the CAMLST macro-instruction.
RECAT, the first operand of CAMLST, specifies that a data set be
recataloged. DSNAME, the second operand, specifies the wain storage
location of an area into which you have placed the fully qualified name
of the data set to be recataloged. VOLUMES, the fourth operand,
specifies the main storage location of the volume list you have built.
HOW TO READ A DATA SET CONTROL BLOCK FROM THE VOLUME TABLE OF CONTENTS
You can read a data set control block (DSCB) into main storage by
using the OBTAIN and CAMLST If-acro-instructions. There are two waY3 to
specify the DSCB that you want read: by using the name of the data set
associated with the DSCB, or by using the atsolute track address of the
DSCB.
When you specify the name of the data set, a forroat 1 DSCB is read
into main storage. To read a DSCB other than a format 1 LSCB, you must
specify an absolute track address. <DSCB formats and field descriptions
are contained in the System control Block publication).
18

When a data set name is: specif ied, the 96-byte data portion of the
format 1 DSCB, and the absolute track address of the DSCB are read into
main storage. When the absolute track address cf a DSCB is specified,
the 44-byte key portion and the 96-byte data portion of the DSCB are
read into main storage.
Example: In the following example, the format 1 DSCB for data set A.B.C
is read into main storage. The serial nurrber of the volume containing
the DSCB is 770655.
r---------T-----·-----T-------------------------------------------------,
I Name I Operation I Operand I
~---------+----------+-------~-----------------------------------------i
I I OBTAIN I DSCBABC READ DSCB FOR DATA I
I I Check Exceptional Returns SET A.B.C INTO MAINI
I DSCBABC I CAMLST I SEARCH,DSABC,VOLNUM,WORKAREA STORAGE AREA NAMED I
I DSABC I DC I CL44'A.B.C' WORKAREA. 96-BYTE I
I
VOLNUM I DC I CL6'770655' DATA PORTION IS I
I
WORKAREAI DS I OD READ. THE REST OF I
I I
DS I 350C THE AREA IS USED BYI
I I I THE OBTAIN ROUTINE I
L _________ ~ __________ ~ _________________________________________________ J
The OBTAIN macro-instruction points to the CAMLST macro-instruction.
SEARCH, the first operand of CAMLST, specifies that a DSCB be read into
main storage. DSABC, the second operap.d~ specifies the main storage
location of a 44-byte area into which you have placed the fully
qualified name of the data set whose associated DSCB is to be read.
VOLNUM, the third operand, specifies the main storage location of a
6-byte area into which you have placed the serial nurrber of the volume
containing the required DSCB. WORKAREA, the fourth operand, specifies
the main storage location of a 350-byte work area that is to contain the
DSCB~
After execution of these macro-instructions, the first 96 b~tes of
the work area contain the data portion of the fornat 1 DSCB; the next
five bytes contain the absolute track address of the DSCB. The OBTAIN
routine uses the rest of tht area as a ~ork area.
HOW TO DELETE A DATA SET
You delete a data set stored on direct-access volumes by using the
SCRATCH and CAMLSTmacro-instructions. This caUSES all data set control
blocks <DSCB) for the data set to be deleted, and all space occupied by
the data set to be made available for reallocation. If the data set to
be deleted is sharing a split cylinder, the space will not be made
available for reallocation until all data sets on the split cylinder are·
deleted.
A data set cannot be deleted if the expiration date in the fermat 1
DSCB has not passed, unless you choose to ignore the expiration date.
You can ignore the Expiration date by using the OVRD option in the
CAMLST macro-instruction.
If a data set to be deleted is stored on more than one volume, either
a device must be available on which to mount the volumes, or at least
one volume must be mounted. In addition, all other required volu~es
must l:e serially mountable. Certain volumes, such as the system
residence volume, must always be mounted.
When deleting a data set, you must tuild a complete volume list in
main storage. This volume list consists of volurre pointers for all
volumes on which the data set is stored. The first two bytes of the
list indicate the number of volume pointers that follow. Each 12-byte
Maintaining the Catalog and the Volurre Table of contents 19

volume pointer consists of a 4-tyte device code, a 6-byte volume serial
number, and a 2-byte data set sequence number. The sequence number is
always zero for direct-access volurres. (Device codes are contained in
Appendix B of this chapter.)
Volumes are processed in the order that they appear in the volume
list. Those volunles that are pointed to at the beginning of the list
are processed first. If a volume is not mounted, a rressage is issued to
the operator requesting him to mount the voluroe. You can indicate the
I/O device on which unmounted volumes are to be mounted by loading
register 0 with the address of the UCB associated with the device to be
used. When the volume is mounted, processing continues. If you do not
load register 0 with a UCB address, its contents rrust be zero.
If the operator cannot mount the requested volume, he issues a reply
indicating that he cannot fulfill the request. A condition code is then
set in the last byte of the volume pointer for the unavailable volume,
and the next volume indicated in the volume list is processed or
requested.
Example:
volumes.
In the following example, data set A.B.C is deleted from two
The expiration date in the format 1 DSCB is ignored.
r---------T----------T-------------------------------------------------,
I Name I Operation I Operand I
~---------+----------+-------------------------------------------------~
DELABC
DSABC
VOLIST
SR I
0,0 SET REG 0 TO ZEROI
SCRATCH I DELABC DELETE DATA SET I
Check Exceptional Returns A.B.C. FROM TWO I
CAMLST I SCRATCH,DSABC"VOLIST"OVRD VOLUMES, IGNORING I
DC I CL44' A. B. C' THE EXPIRATION I
DC I B'2' DATE IN THE DSCB. I
DC I X'30002001' 2311 DISK STORAGE I
DC I CL6'000017' VOLUME SERIAL NO. I
DC I H'O' SEQUENCE NUMEER I
DC I X'30002001' 2311 DISK STORAGE I
DC I CL6' 000018' VOLUME SERIAL NO. I
DC I H'O' SEQUENCE NUMBER I
L _________ ~ __________ ~ _________________________________________________ J
The SCRATCH macro-instructicn points to the CAMLST macro-instruction.
SCRATCH, the first operand of CAMLST, specifies that a data set be
deleted. DSABC, the second operand, specifies the main storage location
of a 44-nyte area into which you have placed the fully qualified name of
the data set to be deleted. VOLIST, the fourth operand, specifies the
main storage location of the volunie list you have built. OVRD, the
sixth operand, specifies that the expiration date be ignored in the OSCB
of the data set to be deleted.
HOW TO RENAME A DATA SET
You rename a data set stored on direct-access volumes by using the
RENAME and CAMLST macro-instructions. This causes the data set nanie in
all format 1 data set control blocks (DSCB) for the data set to be
replaced by the new narre that you supply_
If a data set to be renanled is stored on more than one volume, either
a device must be available on which to mount the volumes, or at least
one volume must be mounted. In addition, all other required volumes
must be serially mountable. Certain volumes, such as the system
residence volume, must always be mounted.
When renaming a data set, you must build a complete volume list in
main storage. This volun'e list consists of volume pointers for all
20