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.