Glossary & Command Reference — CA IDMS Crash Course

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Terms

Term	Meaning
ADS/O	Application Development System/Online. A 4GL for building IDMS/DC applications as dialogs and processes. Much legacy business logic lives here rather than in COBOL.
Area	A contiguous range of pages holding one or more record types. The unit of READY, locking, backup and recovery. Logical name in the schema, physical mapping in the DMCL.
ASF	Automatic System Facility. Lets end users define and populate tables inside IDMS without DBA involvement. A common source of data missing from scoping surveys.
Bachman diagram	The standard notation for a network schema: boxes are record types, arrows point owner → member, labelled with the set name.
Buffer pool	In-memory database pages inside the CV. Sized in the DMCL. The largest single performance lever available.
CALC	A location mode: the DBMS randomises a declared key to a target page, giving single-I/O access by key with no index.
CDC	Change data capture. Reading a database's log or journal to replicate committed change continuously.
Central version (CV)	The long-running z/OS address space that owns the database files, serialises requests, manages buffers and locks, and writes journals.
Checkpoint (CKPT)	A journal record marking a durable point for a run unit, written by COMMIT.
CODASYL	Conference on Data Systems Languages. Its Data Base Task Group published the network model specification in 1971; IDMS is its most successful commercial implementation.
Currency	The DBMS's memory of where a run unit is positioned. Four kinds: run unit, record type, set type, area.
DBAN	IDMSDBAN, the database analysis utility. Reports chain lengths, space utilisation, fragmentation and broken pointers.
DBNAME	A named collection of segments a run unit can address as one database. Defined in the DBTABLE.
Db-key	A 32-bit physical address combining a page number and a line index, split at the db-key radix. Unique within a page group. Not stable across a reorganisation.
DC / IDMS-DC	IDMS's built-in teleprocessing monitor: terminals, tasks, program pools, storage pools.
DCMT	The online operator command facility. `DCMT DISPLAY …` interrogates state; `DCMT VARY …` changes it.
DCUF	User command facility — session-level settings such as `DCUF SET DICTNAME`.
DIRECT	A location mode where the program supplies a suggested db-key. Rare and deliberate.
DMCL	Device Media Control Language. The physical definition: segments, files, page sizes, page ranges, buffer pools, journals, db-key radix.
ERU	External run unit — a run unit driven from outside the CV (batch, CICS, JDBC). Counted against MAXERUS.
Fragment	The overflow portion of a record that grew beyond its page. The root stays at the original db-key so pointers remain valid; reading costs an extra I/O.
IDD	Integrated Data Dictionary. An IDMS database describing the installation: schemas, subschemas, records, elements, programs, users.
IDMSBCF	Batch Command Facility — runs SQL and utility statements from JCL.
Journal	The write-ahead log. Disk journal files in rotation, offloaded to archive journals. The source stream for both recovery and log-based CDC.
Line index	The slot directory at the end of a page mapping line numbers to byte offsets, so records can move within a page without invalidating db-keys.
Local mode	A batch job opening the database files directly instead of connecting to the CV. Fast, exclusive, and journalled only on request.
LRF	Logical Record Facility. Subschema-defined flattened records assembled by declared path groups.
MAXERUS	SYSGEN limit on concurrent external run units.
MAXTASKS	SYSGEN limit on concurrent tasks inside the CV.
Membership options	MANDATORY/OPTIONAL (can it be disconnected) × AUTOMATIC/MANUAL (is it connected on STORE). The closest thing IDMS has to declarative referential integrity.
Page group	A namespace for page numbers. Sets cannot span page groups because db-key pointers carry no group qualifier.
Page reserve	Space held back on each page so records that grow can expand in place instead of fragmenting.
Prefix	The block of db-key pointer slots preceding the user data in every record occurrence, one slot per set pointer.
Radix	The number of low-order db-key bits reserved for the line index. Determines maximum records per page and maximum addressable pages.
Record ID	The numeric identity of a record type, stamped into every occurrence and into journal images. The discriminator a capture agent uses.
Run unit	One binding of a program to a subschema. Owns currency, locks and the journal thread. BIND to FINISH.
Schema	The complete logical design: every record type, set type and area. Versioned.
Segment	A named group of areas and their files. The unit of physical administration; carries the page group and radix.
Set	A named, ordered relationship between one owner record type and one or more member record types, materialised as pointer chains or index structures.
Singular set	A set with `OWNER IS SYSTEM`, so exactly one occurrence exists database-wide. Used for standalone indexes and sequential paths.
SMP	Space management page. Records free space for nearby pages so STORE can pick an overflow page without probing.
SR7 / SR8	System record types forming an integrated index: SR7 is the index owner, SR8 blocks hold sorted key entries and pointers.
Subschema	A program's view: which records, elements, sets and areas it may use, and in which usage modes. Bound at runtime.
SYSCTL	A dataset telling a batch job which CV to connect to. Its absence is how a job becomes local mode.
SYSGEN	The CV's own definition: tasks, programs, terminals, pools, limits.
SYSIDMS	A parameter file read by batch jobs: DBNAME, DICTNAME, JOURNAL, LOCAL and more.
UCF	Universal Communications Facility. Lets CICS, TSO or z/VM front-end an IDMS/DC session.
VIA	A location mode clustering a record physically near the owner it will be connected to in a named set. The highest-leverage physical decision in a schema.
Warm start	Automatic recovery on CV restart: in-flight run units are backed out using before-images; committed work stands.

DML verb reference

Statement	Effect
`BIND RUN-UNIT`	Starts the run unit and binds the subschema.
`BIND record-name`	Associates a record type with its work area in the program.
`READY area USAGE mode`	Opens an area in one of RETRIEVAL / PROTECTED RETRIEVAL / EXCLUSIVE RETRIEVAL / UPDATE / PROTECTED UPDATE / EXCLUSIVE UPDATE.
`FIND …`	Locates a record and sets currency. Does not move data.
`GET [record]`	Moves the current of run unit into the work area.
`OBTAIN …`	FIND plus GET.
`OBTAIN CALC record`	Retrieves by the CALC key already moved into the work area.
`OBTAIN record DB-KEY IS x`	Direct retrieval by saved address. One I/O, no navigation.
`OBTAIN FIRST\|LAST\|NEXT\|PRIOR\|n … WITHIN set`	Positional navigation within a set occurrence.
`OBTAIN OWNER WITHIN set`	Retrieves the owner of the current set occurrence.
`OBTAIN NEXT record WITHIN area`	Area sweep in db-key sequence.
`FIND … WITHIN set USING sort-key`	Positions by key within a SORTED set without walking.
`ACCEPT var FROM CURRENCY`	Copies the current db-key into a program variable.
`ACCEPT STATISTICS`	Returns run-unit I/O and lock counters to the program.
`STORE record`	Stores the work area, places by location mode, connects to every AUTOMATIC set using current owners.
`MODIFY record`	Replaces the stored occurrence with the work area. Requires a prior GET/OBTAIN.
`ERASE record`	Erases only if it owns no non-empty set.
`ERASE record PERMANENT`	Erases mandatory members recursively; disconnects optional ones.
`ERASE record SELECTIVE`	As PERMANENT, but also erases optional members that belong to no other set.
`ERASE record ALL`	Erases every member recursively regardless of membership option.
`CONNECT record TO set`	Links the current of run unit into the current occurrence of the set.
`DISCONNECT record FROM set`	Unlinks it. Legal only for OPTIONAL membership.
`IF set-name IS [NOT] EMPTY`	Tests set emptiness with no I/O and no currency change.
`IF record MEMBER\|NOT MEMBER set`	Tests whether the current record is connected to the set.
`KEEP [EXCLUSIVE] CURRENT`	Explicit shared or exclusive lock on the current record.
`COMMIT [ALL]`	Checkpoints and releases locks. ALL retains currencies.
`ROLLBACK [CONTINUE]`	Backs out to the last checkpoint. CONTINUE leaves the run unit active.
`FINISH`	Ends the run unit, commits, releases areas and locks.

Error-status conditions

A status is four characters: a two-digit major code identifying the verb and a two-digit minor code identifying the condition. The minor codes below are the ones you will meet constantly. Confirm exact major-code pairings for your release in the CA IDMS Messages and Codes manual.

Status	Condition
`0000`	Successful.
`0307`	End of set, area or index. The normal loop terminator, tested as `DB-END-OF-SET`.
`0326`	Record not found — no occurrence matches the CALC key. Tested as `DB-REC-NOT-FOUND`.
`xx05`	Record, set or area is not in the subschema.
`xx06`	Currency was not established for the named record, set or area.
`xx12`	Duplicate key where duplicates are not allowed.
`xx29`	Record is the owner of a non-empty set — plain ERASE rejected.
`xx66`	Area not readied in the usage mode the verb requires.
`3xxx`	Deadlock, timeout and lock-wait family.

Operator & utility commands

Command	Purpose
`DCMT DISPLAY ACTIVE TASKS`	What is running in the CV right now.
`DCMT DISPLAY STATISTICS SYSTEM`	Task rates, waits, storage high-water marks.
`DCMT DISPLAY BUFFER`	Buffer pool sizes, reads, writes, hit ratios.
`DCMT DISPLAY AREA area-name`	Area status, lock mode, current users.
`DCMT VARY AREA area-name OFFLINE`	Quiesce an area for a reorg or consistent copy.
`DCMT DISPLAY JOURNAL`	Journal file status and archive state.
`DCMT DISPLAY LOCKS`	Lock holders and waiters.
`DCUF SET DICTNAME name`	Point the session at a dictionary.
`DISPLAY SCHEMA … WITH ALL`	Punch the full schema definition from the dictionary — the metadata extract for target DDL generation.
`DISPLAY ALL PROGRAMS WHICH USE RECORD …`	Impact analysis from the dictionary's dependency graph.
`BACKUP` / image copy	Physical copy of an area; the base for a rollforward.
`RESTORE`	Puts an image copy back. A replication event.
`UNLOAD` / `RELOAD`	Logical unload and reload for reorganisation. Reassigns every db-key.
`PRINT PAGE`	Hex dump of a page with structural interpretation. The forensic tool.
`IDMSDBAN`	Analysis: space, chain lengths, fragmentation, broken pointers.
`IDMSBCF`	Batch command facility for SQL and utility statements.
`IDMSRPTS`	Dictionary cross-reference and documentation reports.

COBOL data types on the wire

Declaration	Storage	Trap
`PIC X(n)`	n bytes of EBCDIC	Space-padded — decide once whether the target trims
`PIC 9(n)`	n bytes, zoned decimal	Unsigned; leading zeros are significant as characters
`PIC S9(n)`	n bytes, sign in the zone nibble of the last byte	Sign overpunch — `-123` ends in `X'D3'`, the letter L
`PIC S9(n)V9(m) COMP-3`	⌈(n+m+1)/2⌉ bytes packed	Sign nibble C/D/F; destroyed by character conversion
`PIC S9(n) COMP`	2, 4 or 8 bytes, big-endian two's complement	Byte order on little-endian consumers
`COMP-1` / `COMP-2`	4 / 8 byte floating point	Traditionally hexadecimal float, not IEEE 754 — confirm which
`OCCURS n TIMES`	Fixed repeating group	Model as a child table with a sequence, not n columns
`OCCURS DEPENDING ON`	Variable-length repeating group	Fixed-offset parsing breaks for every record below maximum size
`REDEFINES`	Alternative interpretations of the same bytes	The discriminator lives in application code, not in the data