Module files 

Files. ASSIGN names a DD, and only the operator maps a DD to a host file, as JCL does, so a program reaches no file it was not given. A binary DD holds z/OS records byte for byte: fixed-length records back to back, or variable-length records each behind a 4-byte RDW. A text DD holds UTF-8 lines, converted through the program’s code page. Sequential files stream; indexed and relative files are held in memory (see Keyed).

Structs

Dd

Dds

The DDs a run may use: given explicitly, or read from DD_<NAME> in the environment.

Found

A record READ found.

KeySpan

Where a key lies in a record.

Keyed

An indexed or relative file, or a sequential file opened I-O, held in memory from OPEN to CLOSE. The DD holds the records in key (or record-number) order, as an IDCAMS REPRO unload of a KSDS or RRDS does, and CLOSE writes them back that way when they changed.

Open

Enums

Format

Keying

How the records of a file held in memory are keyed. Record numbers and positions are held as eight big-endian bytes, so that they sort.

Record

What a READ found.

Constants

MAX_RELATIVE

The highest relative record number: past it WRITE is a boundary violation (status 24). It stands in for the space a cluster is defined with, so that a stray record number cannot make CLOSE write millions of empty slots.

Functions

absent

An OPTIONAL input file with no DD: every READ is at end.

number_of

open

open_keyed

Opens a file held in memory. With no DD (an OPTIONAL file) or no file at the DD’s path, it starts empty; OUTPUT always starts empty. record_len is the longest record.

record_number