Name the different lookup cache(s)?
• Informatica lookup are of two types.
Here,cached lookups can be sytatic or dynamic.
Lookup cache can be persistent or non-persistent.
• The different lookup cache(s) are:
• Persistent cache:
Persistent cache enables to save the lookup cache files and also reuse them the next time the informatica server processes a lookup transformation configured to use the cache.
• Recache from database:
It is possible to configure the lookup transformation to rebuild the lookup cache , if the persistent cache is not synchronized with the lookup table.
• Static cache:
It is possible to configure a static or read only cache for only lookup table.
By default informatica server creates a static cache. It caches the lookup table and lookup values in the cache for each row that comes into the transformation.
• Dynamic cache:
For cache the target table and insert new rows into cache ,then a lookup transformation to use dynamic cache is created .The informatica server dynamically inserts data to the target table.
• Shared cache:
It is possible to the lookup cache between multiple transactions.The unnamed cache between transformations in the same mapping can also be shared.
Types of Lookup Caches in Informatica
|Lookup Caches in Informatica||Static cache|
Static Cache is same as a Cached Lookup in which once a Cache is created the Integration Service always queries the Cache instead of the Lookup Table.
In Static Cache when the Lookup condition is true it return value from lookup table else returns Null or Default value. In Static Cache the important thing is that you cannot insert or update the cache.
In Dynamic Cache we can insert or update rows in the cache when we pass the rows. The Integration Service dynamically inserts or updates data in the lookup cache and passes the data to the target. The dynamic cache is synchronized with the target
When we use shared Cache Informatica server creates the cache memory for multiple lookup transformations in the mapping and once the lookup is done for the first lookup then memory is released and use that memory used by the other look up transformation.
We can share the lookup cache between multiple transformations. Unnamed cache is shared between transformations in the same mapping and named cache between transformations in the same or different mappings.
If we use Persistent cache Informatica server processes a lookup transformation and saves the lookup cache files and reuses them the next time. The Integration Service saves or deletes lookup cache files after a successful session run based on whether the Lookup cache is checked as persistent or not
In order to make a Lookup Cache as Persistent cache you need to make the following changes
- Lookup cache persistent: Needs to be checked
- Cache File Name Prefix: Enter the Named Persistent cache file name
- Re-cache from lookup source: Needs to be checked
Recache from database
If the persistent cache is not synchronized with the lookup table you can configure the lookup transformation to rebuild the lookup cache.