Auto Memory Settings in Session Level
The session have settings for Maximum Memory Allowed for Auto
Memory Attributes and Maximum Percentage Allowed for Auto Memory Attributes.
Whichever is smaller is the amount used for items like the DTM buffer size,
lookup cache, and other settings. The default is 512MB and 5% of the available
server memory, whichever is smaller.
Tuning these values can make a huge impact on performance of the
session, with a very small change that needs little testing and does not create
mapping logic changes that require more extensive testing.
Testing Auto Memory settings requires knowing the amount of
available memory, the number of concurrent jobs that might be running along
with the session in question, and some adjustments and sample runs to find out
if adding memory helps or not. The usual method for tuning is the increase the
setting until such time as more memory has not impact and then scale back. Set
the memory settings within reason, because the job is not likely to always run
without any other system jobs, and there must be enough memory to support
operating system processes and any other applications that are running, as well
as the Informatica jobs.
The settings are set in the Session Configuration in the Config
Object Tab. It affects all of the items that use “Auto” as the memory value,
including DTM Size, DTM Buffer Block Size, cache index and data sizes for
Lookups, Sorters, Aggregators, etc. Sometimes those specific settings should be
set to values independent of Auto Memory values, but typically only if it will
make the value larger than the Auto Memory setting, not if it will be smaller.