Cache in Informatica

What do you mean by Index cache and Data cache ?Explain it ?

1)Informatica server create Index and Data cache for Aggregator, Rank, Joiner, Look up Transformations.

2)Informatica server stores key values in Index cache,   and output values in data cache.

3)Informatica server  create cache files based on Informatica Server Code Page.

4)If Informatica server require more memory, it stores overflow values in cache files. If session completes server      releases cache memory and deletes cache files.

Transformation	Index Cache	Data Cache
Aggregator	Stores group values as configured in the Group-By ports.	Stores calculations based on the Group-By ports.
Rank	Stores group values as configured in the Group-By ports.	Stores ranking information based on the Group-By ports.
Joiner	Stores index values for the master source table as configured in the join condition.	Stores master source rows.
Lookup	Stores lookup condition information.	Stores lookup data that is not stored in the index cache.

Cache files located in which directory?

Informatica server locate index and data cache files in $PMCacheDir .

For index cache file it store with *.idx format and  for data cache file *.dat.

After successfully executing session Informatica server delete index and data cache files.

 

Cache in Informatica

Explain Briefly about Session Caches?

Aggregator Cache, Rank Cache, Lookup Cache, Joiner Cache.

Aggregator Cache : 

When the Informatica Server runs a session with an Aggregator transformation, it stores data in memory until it completes the aggregation. When you partition a source that uses an Aggregator transformation, the Informatica Server creates one memory cache and one disk cache for each partition. It routes data from one partition to another based on group key values of the transformation

Rank Cache: 

When the Informatica Server runs a session with a Rank transformation, it compares an input row with rows in the data cache. If the input row out-ranks a stored row, the Informatica Server replaces the stored row with the input row.

Joiner Cache:

When the Informatica Server runs a session with a Joiner transformation, it reads all the rows from the master source and builds memory caches based on the master rows. After building these caches, the Informatica Server reads rows from the detail source and performs the joins.

The Informatica Server creates the index cache as it reads the master source into the data cache. The Informatica Server uses the index cache to test the join condition. When it finds a match, it retrieves row values from the data cache. 

To increase join performance, the Informatica Server aligns all data for joiner caches on an eight byte boundary.

Lookup Cache:

The Informatica Server builds a cache in memory when it processes the first row of data in a cached Lookup transformation. It allocates memory for the cache based on the amount you configure in the transformation or session properties. The Informatica Server stores condition values in the index cache and output values in the data cache. The Informatica Server queries the cache for each row that enters the transformation.

What is meant by Incremental Aggregation where it can be used?

Incremental Aggregation is used to improve session performance It is used only if source changes incrementally between sessions, and capture those incremental changes.