Lookup Cache

A Lookup transformation would be used in an Informatica mapping to lookup data in a relational table, view, or synonym. The Informatica server queries the lookup table based on the lookup ports in the transformation. It compares Lookup transformation port values to lookup table column values based on the lookup condition. The result of the Lookup would then be passed on to other transformations and targets. A Lookup transformation can be configured to be either cached or uncached Advantages of Lookup caches  Improves the session performance since the Informatica server queries the lookup table instead of the Lookup cache that’s present on the server itself. This would prevent the server from hitting the (Lookup table that is present on the) database for each record that is processed and hence increase the performance. A lookup cache can be further configured to be either static or dynamic. Static cache or read-only cache  Remains static and does not change during the session, i.e the Informatica server cannot insert or update the cache. This is the default cache that is created by the Informatica server.  Since Informatica cannot insert or update a static Lookup cache, when the Lookup does not find a record in the Lookup table, it would return a default value for connected Lookups and a NULL for unconnected Lookups.  This can be created for any lookup table. Dynamic cache:  In case the Lookup does not find a record in the Lookup table, the Informatica server would insert the record into the Lookup cache and passes data to the target table too.  This is used only when a lookup is done on a target table. Non-persistent cache:  By default, the Informatica Server uses a non-persistent cache in which case the Informatica server would delete the cache files at the end of the session. Persistent cache:  When the cache is configured to be persistent, the Informatica server would save the cache files to the disk, the first times it runs the session. The next time the

Informatica server runs the session, it builds the memory cache from the cache files.  If the Lookup table changes, the lookup cache has to be recached from the database by overriding the session properties (by using the recache from database option)  If the Informatica server cannot reuse the cache and cannot recache the lookup from the database, it fails the session. Lookup Cache Directory Name  The directory used to build the lookup cache files when the Lookup transformation is configured to cache the Lookup table Lookup data cache size  The maximum size the Informatica server allocates to the data cache in memory which is 2,000,000 bytes by default.  This can be changed as required.  When the server cannot store all the data cache in memory, it pages it to the disk.  The Server would fail the session if it cannot allocate the configured amount of memory when initializing the session. Lookup Index cache size  The maximum size the Informatica server allocates to the index cache in memory which is 1,000,000 bytes by default.  This can be changed as required.  When the server cannot store all the index cache in memory, it pages it to the disk.  The Server would fail the session if it cannot allocate the configured amount of memory when initializing the session.