Directing assembler messages to your terminal: SYSTERM

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Define the data set that contains your terminal message's output with the SYSTERM DD statement: 
//SYSTERM  DD   SYSOUT=A
On TSO, the terminal messages can be sent to your terminal by using the following ALLOC statement: 
ALLOC F(SYSTERM) DA(*)

This data set is used by the assembler to store a condensed form of SYSPRINT containing flagged statements and their associated error messages. It is intended for output to a terminal, but can also be routed to a printer, a magnetic tape, or a direct-access storage device. Depending on the ASA option, the assembler uses ASA or machine control characters to skip to a new line for this data set.