The DTM process creates in-memory index and data caches to temporarily store data used by the following transformations:
Aggregator transformation (without sorted input)
Lookup transformation (with caching enabled)
You can configure memory size for the index and data cache in the transformation properties. By default, the PowerCenter Integration Service determines the amount of memory to allocate for caches. However, you can manually configure a cache size for the data and index caches.
By default, the DTM creates cache files in the directory configured for the $PMCacheDir service process variable. If the DTM requires more space than it allocates, it pages to local index and data files.
The DTM process also creates an in-memory cache to store data for the Sorter transformations and XML targets. You configure the memory size for the cache in the transformation properties. By default, the PowerCenter Integration Service determines the cache size for the Sorter transformation and XML target at run time. The PowerCenter Integration Service allocates a minimum value of 16,777,216 bytes for the Sorter transformation cache and 10,485,760 bytes for the XML target. The DTM creates cache files in the directory configured for the $PMTempDir service process variable. If the DTM requires more cache space than it allocates, it pages to local cache files.
When processing large amounts of data, the DTM may create multiple index and data files. The session does not fail if it runs out of cache memory and pages to the cache files. It does fail, however, if the local directory for cache files runs out of disk space.
After the session completes, the DTM releases memory used by the index and data caches and deletes any index and data files. However, if the session is configured to perform incremental aggregation or if a Lookup transformation is configured for a persistent lookup cache, the DTM saves all index and data cache information to disk for the next session run.