CA IDMS/DB Schema and VSAM File Correspondences › Area and File Considerations

Area and File Considerations

To represent a VSAM data structure in the CA IDMS/DB database, you must specify the area in which you want the data to reside. Additionally, you must associate the area with an CA IDMS/DB file, and assign the file to an external ddname (z/OS) or filename (z/VSE).

More information:

Instructions for defining areas and files are presented in CA IDMS Database Administration Guide.

Design Considerations

The following design considerations apply to schema area and file definitions for VSAM data structures:

• You can put any number of CA IDMS VSAM Transparency files in the same CA IDMS/DB area, as long as you have space for these files. If you put more than one CA IDMS VSAM Transparency file in the same area, each file will be readied in the same usage mode.

  Note: For optimal performance, you should put only one CA IDMS VSAM Transparency file in an area.

• Each ddname (z/OS) or filename (z/VSE) must be unique for an application program. This means that the external file name specified in the ASSIGN TO clause of the physical database DDL FILE statement must be different than the file name used in the VSAM application.

  For example, suppose a VSAM application program contains the following COBOL SELECT statement:

  SELECT CUSTFILE ASSIGN TO SYS030.
  

  You could code the following file assignment:

  ADD FILE CUSTOMER-FILE ASSIGN TO CSTFILE.
  

  The JCL for running the VSAM application in local mode will include one DD or DLBL statement for each of the files described above:

  //SYS030 DD SUBSYS=(ESVS,'FMT=fmtname','SUBSCHEMA=ssname', ... )
  //CSTFILE  DD DSN=CUST-FILE,DISP=SHR
  

More information:

For more information on CA IDMS/DB database definition, refer to CA IDMS Database Administration Guide.