IBM OS/390 User Manual

A. VSE: With Tapemark Before Data Records

┌─────┬───────────────────┬─────┬─────┐
│ TM

│ Data Records 1-n

│ TM

│

└─────┴───────────────────┴─────┴─────┘

B. VSE: Without Tapemark Before Data Records

┌───────────────────┬─────┬─────┐
│ Data Records 1-n

│ TM

│

└───────────────────┴─────┴─────┘

1. On input, IOCS can handle files with or without a

tapemark preceding the data records.

2. For multivolume files, only one tapemark is written

at the end of each volume except the last. Two tapemarks
follow the data records on the last volume.

C. VSE: Multifile Volume

I----FILE A-----I

I----FILE B-----I

I----FILE C-----I

┌─────┬───────────────┬─────┬───────────────┬─────┬───────────────┬─────┬─────┐
│ TM

│ Data Records

│ TM

│ Data Records

│ TM

│ Data Records

│ TM

│

└─────┴───────────────┴─────┴───────────────┴─────┴───────────────┴─────┴─────┘

D. OS/390: Single Data Set-Single Volume

┌────────────┬─────┬─────┐
│ Data Set A │ TM

│ TM

│

└────────────┴─────┴─────┘

E. OS/390: Single Data Set-Multiple Volumes

┌─────────────────────┬─────┐
│ Data Set A - Part 1 │ TM

│

└─────────────────────┴─────┘

┌────────────────────────┬─────┐
│ Data Set A - Last Part │ TM

│

└────────────────────────┴─────┘

Figure 7. Nonstandard Labels Supported by VSE

When analyzing VSE programs supporting nonstandard labeled tape files used
under OS/390, you must:

1. Create nonstandard label processing routines for input header labels, input

trailer labels, output header labels and output trailer labels.

2. Insert the installation

′

s routines into the system by including predefined

member names into SYS1.LPALIB as type4 SVC routines. (See

Using

Magnetic Tapes, GC26-4923.)

3. Code NSL in the job control LABEL parameter of the DD statement for the

tape data set at execution time.

The first two items define the programming effort to be considered in the design
and writing of the installation

′

s nonstandard label routines. Once these routines

have been made a part of the SVC library, they are used by all application
programs with tape data sets defined by LABEL=(,NSL).

The conventions, requirements, and techniques for writing OS/390 nonstandard
label routines differ from the individual label processing subroutines used under
VSE.

Chapter 5. Disk and Tape Storage Considerations

107