Caching Transform Data
The Transformation Editor’s Caching tab gives you access to set up several of the standard TDV caching features. Because TDV treats transforms as if they were procedures, the caching features that you can enable are the features that are generally supported for other TDV procedure resources. For information on caching with TDV, see
TDV Caching.
The procedure caching process uses one storage table for each output cursor and an additional storage table for any scalar outputs. For example, a procedure with two INTEGER outputs and two CURSOR outputs would use three tables:
• One for the pair of scalars
• One for the first cursor
• One for the second cursor
If a procedure has input parameters, the cached results are tracked separately for each unique set of input values. Each unique set of input parameter values is called a variant.
A procedure cache that uses non-null input parameters must be seeded with at least one variant from a client application other than Studio, for the Cache Status to change from NOT LOADED to UP. Using the Refresh Now button does not change the status of a cache that is not loaded. Even if procedure caching configuration is correct, the status does not show that it is loaded until a client seeds the cache.
When a procedure cache is refreshed, all the cached variants already in the table are refreshed. If no variants have yet to be cached, then nothing is refreshed or only the null input variant is refreshed. You can refresh a procedure cache from Studio or using the RefreshResourceCache procedure. (See the TDV Application Programming Interfaces Guide.)
To define a cache for your transform
1. Open your transform.
2. Validate that the input parameter values for your transformation do not exceeds 255 characters.
If the parameter exceeds 255 characters, the procedure call is not cached. Instead, it is executed as if caching was disabled. TDV tracks procedure variants by converting the input parameter values are to a string to compare for uniqueness.
3. Select the Caching tab.
4. Click Create Cache.
5. Define the cache.
See the TDV User’s Guide for more information on caching concepts and how to define caching on a procedure.
6. Save your transform.
7. Optionally, configure the Maximum number of procedure variants field in the Advanced section of the Caching panel to store the variant result sets produced from your transforms.
By default, the maximum number of stored variants is 32. If the cache is full, the least recently used variant is swapped out for the latest variant.