Performance Monitoring in a Time-Sharing System
A software measurement facility which is part of
a general purpose time-sharing system is described. 
 The Date Collection Facility (DCF) has been implemented
in the Michigan Terminal System (MTS) for the 
System/360 model 67.  It exists for the purpose of monitoring
operating system and user program behavior 
and performance.  The overall structure of MTS is outlined
in order to explain the implementation of 
the DCF.  Events in the system are identified and recorded
from within the supervisor, and dumped to 
magnetic tape by an auxiliary program for off-line processing.
 Events in user programs which are unrelated 
to system actions are recorded with a supervisor call.
 The time of occurrence of each event is accurately 
recorded, and data items are further identified by job and
type.  The overhead associated with data collection 
and its interference with normal jobs is carefully analyzed,
and both are shown to be minimal.  Several 
examples are given of information obtained with the
facility and of applications in which it has been 
useful.  Some general guidelines are offered for
the construction of future monitoring programs.
CACM November, 1969
Pinkerton, T. B.
