IBM Mainframe Forum

Hi Guys,

What is the difference between SYSIN and SYSTSIN. I checked a post where it is described as

SYSTSIN is the standard input DD (i.e. Terminal Input) for either the TSO program (IJKEFT**) or the REXX interpreter (IRXJCL).

SYSIN is a standard input DD, usually used to supply run-time parameters to the associated program.

So, is it correct or is there anything else which is missing here... I was checking IBM manual where SYSTSIN was described as

The SYSTSIN DD statement is used to specify that the data to follow consists of executable commands and/or subcommands. For example, to indicate to the system that all data following this statement is to be used as input, until the system encounters an input delimiter, such as the characters /* or the DLM operand,

but we put commands in SYSIN as well..

Can anyone please clarify me..

nikesh_rai wrote:... but we put commands in SYSIN as well..

Can anyone please clarify me..

The purpose of the contents of any data set depends on the program. The IKJEFT01 program, for example is the TSO "Terminal Monitor Program." When it is run in batch, IKJEFT01 expects the data set specified by DD name SYSTSIN to contain input it understands, that is TSO commands as well as member names of Rexx execs or TSO CLISTs located in data sets specified by DD name SYSPROC or SYSEXEC.

Other programs have different requirements. Cobol compilers, for example, generally expect the data set specified by the SYSIN DD statement to contain the source of a Cobol program. Nothing else. Sort programs, on the other hand, expect the data set specified by the SYSIN DD statement to contain control instructions (often constructed as "commands" and sometimes called "commands") so it can sort data contained in other data sets. It all depends on the program. That's the best explanation I can do.

thanks Steve for clarification..

Hi Steve
Could you please explain in simple terms. What I have got that SYSTIN is used for IKJEFT01 program and SYSIN for some another program. Apart from this SYSTIN can also be used with REXX interpreter but not SYSIN. Please correct me if wrong.

BigIronGuy wrote:Hi Steve
Could you please explain in simple terms. What I have got that SYSTIN is used for IKJEFT01 program and SYSIN for some another program. Apart from this SYSTIN can also be used with REXX interpreter but not SYSIN. Please correct me if wrong.

//SYSTSIN is the standard DD name used by the program IKJEFT01 (and some others) to get its own commands from. Usually those commands make the IKJEFT01 to call other programs (aka load modules) which often are written in various languages, from Assembler to REXX. Each of those “internal” programs=load modules can use (and often does) its own one or more DD names for its own input/output operations. Many typical programs called from inside of IKJETF01 are using the DD name //SYSIN as its main input data source. This depends exclusively on: what DD name has been chosen by the program developer? Since most of program codes are copied (or stolen) by one developer from another one, so very often the same DD name is used by many different programs; especially - //SYSIN DD.