That can be accomplished in conjunction with CICS transaction classes.
If a CICS TCLASS definition is created for the purpose of monitoring, the desired transaction can be defined to the new class. CICS will then maintain the number of concurrent transactions in that class. SYSVIEW can monitor the transaction class using the metric TCLSACT.
A very high MAX or LIMIT value can be specified on the TCLASS definition is an active limit is not desired.
Setting the Msg to Yes will send a message to the Log when the Threshold Pops.