This model analyses a queuing system with a fixed population with members that periodically require servicing. Although we model a computer timesharing system in this example, this model is typically referred to as the machine repair problem, because one can think of it as applying to a group of machines periodically requiring repair by a number of service personnel. A detailed discussion of this model may be found in Developing More Advanced Models.

MODEL:

 ! Model of a computer timesharing system;

 ! The mean think time for each user (more

   generally, Mean Time Between Failures in a

   repair system);

   MTBF = 40;

 ! The mean time to process each compute request

   (more generally, Mean Time To Repair in

   seconds);

   MTTR =  2;

 ! The number of users;

   NUSER = 32;

 ! The number of servers/repairmen;

   NREPR = 1;

 ! The mean number of users waiting or in service

   (more generally, the mean number of machines

   down);

   NDOWN =

    @PFS( MTTR * NUSER/ MTBF, NREPR, NUSER);

 ! The overall request for service rate (more

   generally, overall failure rate), FR, must

   satisfy;

   FR = ( NUSER - NDOWN)/ MTBF;

 ! The mean time waiting for or in service (more

   generally, the mean time down), MTD, must

   satisfy;

   NDOWN = FR * MTD;

END

Model: EZMREPAR