Tandem Capacity Model (TCM) Manual

• Calculate batch response times with completed jobs removed from system
• CPU tunability
The first three parameters, Number of Batch CPUs, and Hardware utilization thresholds for CPU
and Disk, and Calculate Batch response times with completed jobs removed from system are found
on the TCM Parameters screen. The last field is found on the Actual or Plan Baseline Detail by
Category screen in the Performance model.
The fourth is not a parameter but a column. For more information about CPU tunability, see “CPU
Tunability” (page 102).
Number of Batch CPUs
The Number of Batch CPUs field indicates the number of CPUs available for batch activity. The
parameter has no effect on OLTP. OLTP processing is always assumed to take place on all CPUs.
It is assumed that both batch and OLTP activity occur in a batch CPU. The default is All, which
means batch activity can run in all CPUs in the system.
Change this field if you limit batch activity to run in a subset of the CPUs in your system. For
instance, if batch activity occurs in CPUs 5 and 6 only, change the Number of Batch CPUs to 2.
Only two CPUs are available for batch activity, and all CPUs are used for OLTP transactions.
All users can modify the Number of Batch CPUs field in the TCM Parameters screen. Figure 31
(page 103) shows a sample TCM Parameters screen.
Hardware Utilization Thresholds for CPU and Disk
The Hardware Utilization Thresholds fields indicate the system resources available for batch
transactions. The default is 100 percent for CPU utilization and 50 percent for disk utilization.
When batch activity is running in a CPU, the CPU can run at 100 percent utilization. When batch
activity is running in a disk, TCM assumes the disk can run at no more than 50 percent utilization.
You need to evaluate both of the default values and determine hardware utilization thresholds
appropriate to your system. For example, if you observe that your disks run at no greater than 40
percent busy, change the disk utilization threshold to 40 percent.
Calculate Batch Response Times With Completed Jobs Removed From System
The Calculate Batch Response Times With Completed Jobs Removed From System field indicates
how TCM should calculate batch response times. The default is TRUE. When the field is set to TRUE,
completed batch jobs are effectively removed from the system. The remaining jobs speed up
because fewer active jobs are sharing the CPU and Disk resources. When the field is set to FALSE,
completed batch jobs are not removed from the system. In this case, TCM treats all batch jobs as
though they restart when completed and assumes that all batch jobs are running simultaneously,
no matter how long they actually take.
All users can modify the Calculate Batch response times with completed jobs removed from the
system field in the TCM Parameters screen. Figure 30 (page 102) shows a sample TCM Parameters
screen.
Differences in Modeling Batch Transactions 101