Peter,
The MATCHLIMIT parameter can be changed from the default of NONE, in the Sysview.CNM4BPRM parmlib member CEITRACE. There are multiple sections in this
parmlib member for setting Default Definition Values and Exec Interface Trace Definitions. Make sure that the changes you make are above the )EOF statement, or the
definition will not be honored as it will be ignored.
As to the reason why setting MATCHLIMIT to NONE is not recommended, it is because MATCHLIMIT=NONE will allow the trace to remain active until it is disabled.
Hence, having that tracing active for protracted periods of time in a production environment could cause overhead to increase.