&SYSIN_DSN System Variable Symbol

Use &SYSIN_DSN in a macro definition to obtain the name of the data set from which the assembler is reading the source module.

The local system variable symbol &SYSIN_DSN is assigned a read-only value each time a macro definition is called.

z/OS

If concatenated data sets are used to provide the source module, &SYSIN_DSN has a value equal to the data set name of the data set that contains the open code source line of the macro call statement, irrespective of the nesting depth of the macro line containing the &SYSIN_DSN reference.

When the assembler runs on the z/OS operating systems, the value of the character string assigned to &SYSIN_DSN is always the value stored in the JFCB for SYSIN.

z/VM

When the assembler runs on the CMS component of the z/VM operating systems, the value of the character string assigned to &SYSIN_DSN is determined as follows:

Table 1. Contents of &SYSIN_DSN on CMS
SYSIN Allocated To:	Contents of &SYSIN_DSN:
CMS file	The 8-character file name, the 8-character file type, and the 2-character file mode of the file, each separated by a space
Reader	`READER`
Terminal	`TERMINAL`
Labeled tape file	The data set name of the tape file
Unlabeled tape file	`TAPn`, where n is a value from 0 to 9, or A to F.

z/VSE

When the assembler runs on the z/VSE operating system, the value of the character string assigned to &SYSIN_DSN is determined as follows:

Table 2. Contents of &SYSIN_DSN on z/VSE
SYSIPT Assigned To:	Contents of &SYSIN_DSN:
Job stream (SYSIPT)	`SYSIPT`
Disk	The file-id
Labeled tape file	The file ID of the tape file
Unlabeled tape file	`SYSIPT`

Examples:

On z/OS, &SYSIN_DSN might be assigned a value such as:

IBMAPC.ASSEMBLE.SOURCE

On CMS, &SYSIN_DSN might be assigned a value such as:

SAMPLE   ASSEMBLE A1

Notes:

If the SOURCE user exit provides the data set information then the value in &SYSIN_DSN is the value extracted from the Exit-Specific Information block described in the section "Exit-Specific Information Block" in the HLASM Programmer's Guide.
The value of the type attribute of &SYSIN_DSN (T'&SYSIN_DSN) is always U.
The value of the count attribute of &SYSIN_DSN (K'&SYSIN_DSN) is equal to the number of characters assigned as a value to &SYSIN_DSN. In the previous CMS example, the count attribute of &SYSIN_DSN is 20.
Throughout the use of a macro definition, the value of &SYSIN_DSN is considered a constant.