6. DATA SOURCES › 6.8 PR/SM LPAR Concepts › 6.8.4 Interpreting PR/SM Data › 6.8.4.3 Logical Partition Interaction › 6.8.4.3.1 Dispatching Frequency

6.8.4.3.1 Dispatching Frequency

If the time slice is not explicitly specified by the user, it
is calculated by the LPAR dispatcher.  This dynamically
calculated value is not recorded in the type 70 subtype 1
record.  Although we know from IBM documentation the formula
that is used, a change to the formula would be impossible to
detect from the information recorded by RMF.  If it does
change, any programs or procedures based on the formula will
require modification.  Since the time-slice value changes
only when partitions are activated or deactivated, or when
logical processors or central processors are varied online or
offline, we can expect this to happen relatively
infrequently.  However, the length of the dynamically
determined time slice is actually a maximum value.  Unless a
partition is wait-enabled, the time slice for dispatching one
of its LPs ends immediately upon an attempt to put the
central processor into the wait state.

If the count of the dispatch events were known, it would then
be possible to calculate the average time slice, which would
likely vary considerably from the dynamic time-slice value.
Without this number, it is impossible to quantify some of the
effects of logical processor dispatching.  This includes the
effective slowing of processor execution speed and I/O
operations.