The ZTCOMMIT command marks the end of a logical transaction within a GT.M program. ZTCOMMIT used with ZTSTART "fences" transactions (that is, marks the end and beginning). Fencing transactions allows the MUPIP JOURNAL facility to prevent incomplete application transactions consisting of multiple global updates from affecting the database during a database recovery.
The format of the ZTCOMMIT command is:
ZTC[OMMIT][:tvexpr] [intexpr]
The optional truth-valued expression immediately following the command is a command postconditional that controls whether or not GT.M executes the command.
The optional integer expression specifies the number of currently open ZTSTARTs for the ZTCOMMIT to close.
A ZTCOMMIT with no argument closes one ZTSTART; in this case, at least two (2) spaces must follow the command to separate it from the next command on the line; with an argument of 0, ZTCOMMIT closes all open ZTSTARTs.
An indirection operator and an expression atom evaluating to a list of one or more ZTCOMMIT arguments form a legal argument for a ZTCOMMIT.
When an application requires sub-transactions, it may nest ZTSTARTs and ZTCOMMITs to a maximum depth of 255. However, a ZTCOMMIT must "close" the outer-most ZTSTART before journaling accepts any part of the "transaction" as complete.