Network Hardware User Manual

458 U3585-J-Z125-8-76

Glossary

time equivalent for the productive performance

In determining the RST (resources service time), a distinction is made between the

CPU and the peripheral devices as follows:

1. For the CPU the RST is the time in which instructions are processed in the TU and

TPR states. This time is called productive CPU RST (the SIH share of the

productive performance is not counted; see above).

2. For the peripheral equipment, the RST is the ﬁrmware service time of the devices

for performing an I/O operation.

The ﬁrmware duration is deﬁned as the time from I/O initiation (START-DEVICE or

START-SUBCHANNEL instruction) to I/O termination (channel interrupt). Only I/O

operations initiated by DMS are counted. This share is called productive I/O RST.

In practical operation, the ﬁrmware duration is affected by other tasks in the system.

The positioning time during disk access, for example, depends on prior events, i.e.

the current arm position, and on operating system strategies. In BS2000, arm

movement optimization is used, i.e. the operating system tries to start I/O accesses

in such a way that arm movements are minimized.

By adding the waiting time of an I/O request in the device queue of the system to the

ﬁrmware duration, the software service time (also called software duration) is obtained.

transaction

Total number of system responses to a user request.

(Please refer to the normal usage in the UTM manuals for the meaning of the term

"transaction" in the UTM reports).