The number of history collections to store in memory. A new
collection begins with the start of each test. The
etsysIpSlaScheduleTable dictates when tests start and stop.
Modifying this value from a larger value to a smaller value
causes the difference to be removed from memory. The
collection with higher index values are removed. The history
collections are found in the etsysIpSlaRttDataTable and the
etsysIpSlaPdvDataTable using a etsysIpSlaCollectionType of
'history'.