Final answer:
To invoke a transaction in CICS, a user needs to type a TRANSID, which is a unique identifier assigned to each transaction. By typing the correct TRANSID, the user can execute the desired transaction and perform the necessary tasks.
Step-by-step explanation:
To invoke a transaction after signing on to CICS, a user needs to type a TRANSID. This is the command used in CICS to initiate a transaction. TRANSID stands for Transaction ID, which is a unique identifier assigned to each transaction in CICS. By typing the correct TRANSID, the user can execute the desired transaction and perform the necessary tasks.