Naming a Master File

Master File names for FOCUS and fixed-format sequential data sources can be up to 64 characters long on z/OS, UNIX, and Windows platforms. Except where noted, this length is supported in all functional areas that reference a Master File.

Using Long Master File Names on z/OS

In the z/OS environment, file and member names are limited to eight characters. Therefore, longer Master File names are assigned eight-character names to be used when interacting with the operating system. Use the following to implement Master File names longer than eight characters:

Member Names for Long Master File Names in z/OS

The DYNAM ALLOC command with the LONGNAME option automatically creates a member for the long Master File name in the PDS allocated to ddname HOLDMAST.

The member name consists of three parts: a prefix consisting of the leftmost characters from the long name, followed by a left brace character ({), followed by an index number. This naming convention is in effect for all long Master Files allocated using DYNAM or created using the HOLD command. The length of the prefix depends on how many long names have a common set of leftmost characters:

  • The first ten names that share six or more leftmost characters have a six-character prefix and a one-character index number, starting from zero.
  • Starting with the eleventh long name that shares the same leftmost six characters, the prefix becomes five characters, and the index number becomes two characters, starting from 00.

This process can continue until the prefix is one character and the index number is six characters. If you delete one of these members from the HOLDMAST PDS, the member name will be reused for the next new long name created with the same prefix.

Long Master File Names and Corresponding Member Names

The following table lists sample long names with the corresponding member names that would be assigned under z/OS.

Long Name

Member Name 

EMPLOYEES_ACCOUNTING
 
EMPLOY{0
 
EMPLOYEES_DEVELOPMENT
 
EMPLOY{1
 
EMPLOYEES_DISTRIBUTION
 
EMPLOY{2
 
EMPLOYEES_FINANCE
 
EMPLOY{3
 
EMPLOYEES_INTERNATIONAL
 
EMPLOY{4
 
EMPLOYEES_MARKETING
 
EMPLOY{5
 
EMPLOYEES_OPERATIONS
 
EMPLOY{6
 
EMPLOYEES_PERSONNEL
 
EMPLOY{7
 
EMPLOYEES_PUBLICATIONS
 
EMPLOY{8
 
EMPLOYEES_RESEARCH
 
EMPLOY{9
 
EMPLOYEES_SALES
 
EMPLO{00
 
EMPLOYEES_SUPPORT
 
EMPLO{01

Implement a Long Master File Name in z/OS

To relate the short name to its corresponding long name, the first line of a long Master File contains the following attribute 

$ VIRT = long_filename

where:

long_filename

Is the long name, up to 64 characters in length.

Allocate a Long Master File Name in z/OS

DYNAM ALLOC DD ddname LONGNAME long_filename DS physical_filename

where:

ddname

Is the one-character to eight-character member name in a PDS allocated to DD MASTER.

long_filename

Is the long Master File name. The DYNAM command creates a copy of the short Master File in the PDS allocated to DD HOLDMAST. The member in HOLDMAST conforms to the eight-character naming convention for long names. The Master File has the $ VIRT attribute on the top line, which contains the long name.

Note: The copy, not the member ddname, is the Master File used when you reference the long name in a request.
physical_filename

Is the data set name of the FOCUS or fixed-format sequential data source.

After you have allocated the long name, you can reference the data source using the long Master File name or the short ddname.

Free an Allocation for a Long Master File Name

DYNAM FREE LONGNAME long_filename

where:

long_filename

Is the long Master File name.

After issuing the DYNAM FREE LONGNAME command, you cannot reference the data source using the long Master File name. However, you can reference it using the short ddname that was specified in the DYNAM ALLOC command.

Using a Long Master File Name on z/OS

To reference the EMPLOYEE data source as EMPLOYEE_DATA, dynamically allocate the long name: 

DYNAM ALLOC DD EMPLOYEE LONGNAME EMPLOYEE_DATA -
  DS USER1.EMPLOYEE.FOCUS SHR REU

You can now issue a request using the long name:

TABLE FILE EMPLOYEE_DATA
PRINT CURR_SAL
BY LAST_NAME BY FIRST_NAME
END

The output is:

LAST_NAME        FIRST_NAME         CURR_SAL
---------        ----------         --------
BANNING          JOHN             $29,710.00
BLACKWOOD        ROSEMARIE        $21,790.00
CROSS            BARBARA          $27,072.00
GREENSPAN        MARY              $9,010.00
IRVING           JOAN             $26,872.00
JONES            DIANE            $18,490.00
MCCOY            JOHN             $18,490.00
MCKNIGHT         ROGER            $16,110.00
ROMANS           ANTHONY          $21,130.00
SMITH            MARY             $13,210.00
                 RICHARD           $9,510.00
STEVENS          ALFRED           $11,010.00

In this example, the long Master File will exist in the HOLDMAST PDS as member EMPLOY{0. The index number after the bracket depends on the number of existing long Master Files containing the same first six leftmost characters. The content of the EMPLOYEE_DATA Master File is virtually identical to the short Master File used in the allocation. The only difference is the $ VIRT keyword on line one, which contains the long name. The FILENAME parameter also contains the long name, up to 64 characters.

$ VIRT=EMPLOYEE_DATA
$ Created from EMPLOYEE      MASTER
FILENAME=EMPLOYEE_DATA,
SUFFIX=FOC
SEGNAME=EMPINFO,  SEGTYPE=S1
 FIELDNAME=EMP_ID,    ALIAS=EID, FORMAT=A9,  $
 FIELDNAME=LAST_NAME, ALIAS=LN,  FORMAT=A15, $
         .
         .
         .

Usage Notes for Long Master File Names

  • The FOCUS Database Server (FDS) is not supported on any platform.
  • The DATASET attribute is not supported in a long name Master File.
  • The ACCESSFILE attribute is not supported with long name Master Files.
  • An external index is not supported.
  • The LONGNAME option of the DYNAM command may only be issued from within a procedure (FOCEXEC) or Remote Procedure Call (RPC). It cannot be used to preallocate long Master Files in JCL or CLISTS.
  • Long Master Files are not designed to be edited on z/OS. Each time the DYNAM command is issued with the LONGNAME attribute, it overlays the existing member in HOLDMAST. You must make any edits (such as the addition of fields or DBA attributes, or use of the REBUILD utility) to an existing short Master File.
  • ? FDT and ? FILE longfilename will show an internal DD alias of @000000n, where n is less than or equal to the number of existing long file allocations. Use this internal DDNAME in all queries that require a valid DDNAME, such as USE commands.