- An access method represents the process that is used to store and retrieve data from the datasets or files.
- Access methods have their own dataset structures to manage data, system-provided programs to define datasets, and utility programs to process datasets.
- Access Method Services (AMS) is a utility mainly used to define and handle VSAM datasets and integrated catalogs.
- IDCAMS(Integrated Data Cluster Access Method Services) is the utility program name for access method services (AMS) and used to create the VSAM datasets.
- The functions of AMS are performed through the different functional commands of IDCAMS.
IDCAMS utility can be invoked in the following three ways -
- Call from the Application program
- Batch mode
- With TSO commands.
Syntax - Batch mode
//JOBNAME JOB job-card-parameters //STEP1 EXEC PGM=IDCAMS //SYSPRINT DD SYSOUT=A //SYSIN DD * AMS commands and their parameters /*
The below are AMS commands of IDCAMS -
|DEFINE||Creates catalogs and catalog entries for files, alternate indexes, paths, and VSAM data spaces.|
|ALTER||Alters the existing catalog entries.|
|LISTCAT||Lists catalog entries.|
|Prints VSAM and nonVSAM files.|
|EXPORT||Creates a copy of a file for backup or makes a file or user catalog portable to use in another system.|
|IMPORT||Reads a backup copy of a file or makes a file or user catalog previously exported available in another system.|
|VERIFY||Provoke a catalog to correctly reflect the end of a file.|
|DELETE||Deletes catalog entries.|
Guidelines for coding commands in IDCAMS -
- At least one blank space must be between the command, the object, and sub-parameter values.
- Sub parameter values can be separated using a space or a comma.
- Space is optional between a parameter and the parenthesis enclosing its values.
- A hyphen (-) is used to specify the current line extended to the following line.
- Multiple parameters can be coded on a line. Still, it is better to place each on a line by itself for better readability.
- A parameter and a sub-parameter cannot be separated from a hyphen. A plus sign should be used for this purpose.
IDCAMS utility is explained in utilities section .