Transaction ID

Every CICS transaction has a short name called the transaction id (trans-id). It is the name the user types and the name CICS uses to find the program.

What is a transaction id

• A transaction id is a 1-to-4 character name that identifies a transaction to CICS.
• It is defined as a TRANSACTION resource — in old systems it lived in the Program Control Table (PCT).
• CICS uses the trans-id to find which program should run first.
• The program can read its own trans-id at run time with EXEC CICS ASSIGN TRANID.

Rules for naming transaction ids

• Only 1 to 4 characters long — no longer names allowed.
• Use letters and digits; the first character is normally a letter.
• Names starting with the letter C are reserved for IBM-supplied transactions — do not use them for your own.
• Keep names short and meaningful, like MNT1 for maintenance or ORD2 for orders.
• One trans-id can be shared by many terminals at the same time; CICS starts a separate task for each user.

IBM-supplied transaction ids you should know

• CESN — sign on to CICS with your user id and password.
• CESF — sign off from CICS.
• CEMT — the master terminal transaction; inquire on and control tasks, programs, files and terminals.
• CEDA — define and change resources online (RDO).
• CETR — control CICS tracing.
• CECI — the command interpreter; lets you test most EXEC CICS commands interactively.

How CICS finds the program

• CICS looks up the trans-id in its resource definitions and reads the PROGRAM name stored there.
• If the trans-id is not found, CICS displays an error and no program runs.
• Example of typing IBM-supplied transaction ids on a clear screen:-
  
  *--- Type these on a clear CICS screen, then press ENTER ---* CESN <-- sign on to CICS CEMT <-- master terminal: check tasks, programs, files CEDA <-- define or change resources online CECI <-- test an EXEC CICS command interactively