The TROLLBACK command terminates a transaction by causing a ROLLBACK, which removes all database updates performed within a transaction. A TROLLBACK without an argument also sets $TLEVEL and $TRESTART to zero (0). Issuing a TROLLBACK when no transaction is in progress ($TLEVEL=0) produces an error.

The format of the TROLLBACK command is:

TRO[LLBACK][:tvexpr] [intexpr]

For an example of the use of the TROLLBACK command, see Chapter 5: “General Language Features of M.