Runtime Considerations › Specifying File Characteristics › Where to Specify File Characteristics

Where to Specify File Characteristics

z/OS

Under z/OS, you can specify a file's characteristics at any of the following levels:

• In the file's associated IDD file entity—Any characteristics you specify here do not have to be specified in the JCL or data set label. However, characteristics specified in IDD are enforced at the other levels; if a characteristic is specified both in IDD and at another level, the IDD specifications take precedence.

  Note: Do not specify a file type or device type at the IDD level. If you specify a characteristic in IDD and you want to change it later, you must recompile all maps that use the file. Therefore, you may not want to provide any characteristics for a file at the IDD level.

• In the JCL—Characteristics you specify in the JCL are enforced at the data set label level.
• As part of the data set's label.

z/VSE

Under z/VSE, you can specify a file's characteristics at either of the following levels:

• In the file's associated IDD file entity—Any characteristics you specify here do not have to be specified in IDMSFILE control statements. However, characteristics specified in IDD are enforced at the IDMSFILE level; if a characteristic is specified both in IDD and at the IDMSFILE level, the IDD specifications take precedence.

  Note: Do not specify a file type or device type at the IDD level. If you specify a characteristic in IDD and you want to change it later, you must recompile all maps that use the file. Therefore, you may not want to provide any characteristics for a file at the IDD level.

• In IDMSFILE control statements—IDMSFILE is a program that enables you to specify file characteristics at runtime in the form of control statements. For a detailed description of IDMSFILE, see z/VSE File Characteristics Program.

Defaults

CA ADS Batch applies defaults to characteristics that are not specified at any level. For physical sequential files, the record format defaults to undefined, the logical record length to 0, and the block size to 6233 for disk files and 32760 for tape files. For VSAM ESDS files, CA ADS Batch uses the information supplied from the catalog.