Set this variable to 1 (on, true, yes) to cause file trace timestamp information to be recorded in the error file. When this variable is enabled, a timestamp is placed at the beginning of every line in the trace file. The format of the timestamp is: HH:MM:SS.mmmmmm, where mmmmmm is the finest resolution that the runtime can obtain from the system. The default setting of this variable is 0 (off, false, no).
Timestamp information is included only when file trace information is directed to a file. Timestamp output can add significant I/O overhead and may have a noticeable impact on performance.