IDCAMS
The utility used to create, list, copy and delete datasets, and the standard tool for anything involving VSAM.
Also written access method services, AMS
IDCAMS is the access method services utility, and it is the one you reach for whenever a dataset itself is the subject rather than its contents.
Its commands read almost like sentences. It defines new datasets, including VSAM clusters and alternate indexes; lists what the catalog knows about a dataset; copies and reorganises data; prints records so you can inspect them; deletes datasets and catalog entries; and repairs entries that have got out of step.
For VSAM it is essentially the only tool. A KSDS is defined with IDCAMS, loaded with IDCAMS, listed with IDCAMS and deleted with IDCAMS, and a program can only use it once that groundwork is done.
The commands go in on SYSIN, usually inline in the JCL, and the report comes back on SYSPRINT with a message for each command and a return code summarising the lot.
Because it both creates and deletes, it is worth reading an IDCAMS step carefully before submitting it, particularly the delete commands, which do exactly what they say.
Related terms
- VSAMA family of dataset types built for fast record access by key, used where applications need to look records up rather than read them in order.
- KSDSThe most common VSAM dataset type, where every record has a unique key used to find it directly.
- Utility programA supplied program that performs a standard job such as copying, sorting, comparing or managing datasets, driven by control statements.
- CatalogThe system's index of where datasets live, so you can refer to a dataset by name without knowing which disk it is on.
- DatasetWhat a mainframe calls a file: a named collection of records with a defined structure, rather than a loose stream of bytes.