Caching Limitations
TDV can cache data from many different sources to many different cache targets. Occasionally, there are subtle limitations when dealing with so many systems. For data caching, those limitations are discussed here.
• The view being cached must NOT have a column called cachekey.
• If the cache target does not support a data type available in the source, then any attempt to store the unsupported data type in the cache results in an error. However, it may be possible to cast the unsupported data type to a supported one (for example, cast a BOOLEAN to an INTEGER type) before sending it to the cache target.
• When caching to a table, ARRAY data types are not supported.
• The following resources cannot be cached without being wrapped in a view or procedure:
— Procedures with no outputs; that is, no data to cache.
— Procedures with input parameters that require the use of cache policies.
— XML files that have been introspected.
— System tables.
— Non-data sources such as folders, and definition sets.
Incremental Caching Limitation
Cache policies cannot be used with incremental caching.
Multi-Table Caching Limitation
Multi-table caching is available for tables and views, not for procedures.
TDV Native Loading Option Database Link Limitations
For database links, the following data type and function support restrictions exist.
Data Source | Cache Target | Data Types Not Supported | Notes |
DB2 | Oracle 11g | REAL, GRAPHIC, LONGVARCHAR, TIME, TIMESTAMP, BLOB, CLOB | CAST, AVG, and SUM functions lose precision |
Sybase ASE 15 | Oracle 11g | TEXT, IMAGE | AVG, COUNT, MAX, MIN, and SUM functions are not supported. |
Oracle 11g | Oracle 11g | BLOB, CLOB AND NCLOB LONGRAW AND LONG | |
SQL Server 2008 | Oracle 11g | NTEXT, TEXT, DATE, IMAGE Oracle treats empty strings as NULL values. | |