Tandem Capacity Model (TCM) Manual

Significant Row
1. Disk Process Priority Queuing—Modifiable by the TCM administrator
Disk Process Priority Queuing shows whether disk process priority queuing is to be applied.
Disk process priority queuing is also known as Mixed Workload Enhancement (MWE) and is
provided for all applications running on NonStop systems using C30 or later product versions
of the operating system. If disk process priority queuing is set to TRUE, the disk process runs
at the priority of its calling process instead of at a higher priority. The value is set according
to the CSV file produced by MeasTCM.
Disk Process Priority Queuing for batch transactions is always set to TRUE because TCM
assumes that applications on pre-C30 systems adequately controlled batch activity so that it
did not interfere with online transactions.
Significant Columns
2. Tunable CPU—Not directly modifiable
To change these tunable CPU values, change them in the Tunable CPU column. (See Figure 41
(page 118).) After TCM recalculates these tunable CPU values, the Workload Detail by Category
screen is updated.
Tunable CPU indicates, for batch transactions only, whether all process category activity occurs
in one or multiple CPUs. It is ignored for online transactions. The process category CPU activity
is either monolithic or spread evenly across all CPUs that are available for batch activity. The
default is Y (yes) for categories that participate in at least one OLTP transaction. The default
is N (no) for categories that participate only in batch transactions.
For example, in the Demo model included with TCM, the Tape Read and Cust Update
categories are not tunable. That is, they are assigned to run in specific CPUs. However, the
FastSort category is tunable. It runs in all CPUs.
3. Priority—Modifiable by the TCM administrator
This column shows the priority assigned to each of the process categories. Interrupts always
have the highest priority.
Changing Process Category Priorities
The Performance model uses process category priority data to calculate response times by using
a priority queueing algorithm. To change specific individual process category priorities, use the
Workload Detail by Category screen in the WA model. You must be the TCM administrator or a
super user to change the individual priorities.
To change process category priorities in the WA model:
1. Open a WA model.
2. Select Options > Change Authorization Level and log on as an administrator or super user.
For more information about this step, see “Changing Authorization Levels” (page 69).
3. Select Find > Workload Detail by Category. Figure 43 (page 123) shows a sample Workload
Detail by Category screen.
4. Select Options > Unprotect Admin Fields. The entries that you can modify are highlighted.
5. Enter the customized priorities in the Priority column for the process categories that you want
to change and press the Return key. To finish entering your data, press Return and then select
Calculate Now or press a function key.
6. Choose Options > Protect Admin Fields.
7. Choose Options > Calculate Now.
8. To save the model, select Save or Save As from the File tab.
122 Workload Apportionment Model