Physical Database DDL Statements › FILE Statements › Entity Currency › Usage

Usage

Dynamic File Allocation Under z/VSE without DYNAM/D

Under z/VSE without DYNAM/D, dynamic file allocation is used only when moving a file to another location while CV remains active. It is not used when a file is initially opened. To open files, CA IDMS/DB requires the external filename, DLBL, and EXTENT for every file defined in the DMCL. Specifying a DSNAME as part of the file's definition is optional and does not affect how a file is opened.

To move a file to a new location while CV remains active, follow this procedure:

1. Deallocate the file using the DCMT VARY FILE command DEALLOCATE option
2. Add or replace the DLBL and EXTENT information in the SYSTEM standard label group using z/VSE batch facilities
3. Re-allocate the file using the DCMT VARY FILE command ALLOCATE option
4. Open the file using the DCMT VARY FILE command OPEN option

Important! Be careful when you replace the DLBL and EXTENT information in the SYSTEM standard label group. The DLBL and EXTENT information affects all other jobs in the z/VSE system that try to open or close database files with the same filename.

Dynamic File Allocation under z/VSE with DYNAM/D

If using DYNAM/D in z/VSE, the functionality related to dynamic file allocation is similar to that provided in z/OS. If a DSNAME is specified as part of the file's definition and no matching external file name is defined in a label group, CA IDMS/DB (in conjunction with DYNAM/D) dynamically allocates the file by creating label and extent information during the open process.

Dynamic File Allocation Under z/VM

If a dynamically allocated file under z/VM is:

• An OS-format data set, the CREATE FILE statement must include the DSNAME, VIRTUAL ADDRESS, and USERID parameters
• A CMS-format file:
  • The file must be a reserved file
  • The CREATE FILE statement must include the VIRTUAL ADDRESS parameter

Dropping a File with Associated Areas

Before you delete the definition of a file, use the ALTER AREA statement to:

• Dissociate the file from any areas with pages that map to the file
• Map the dissociated area pages to one or more other files