The index is stored in index files on disk. When a database is active, the most recently accessed index pages are held in the index cache. How much of the index can be held in memory simultaneously depends on the amount of memory that you allocate to the index cache.
The size of index pages is fixed at 8 K to reduce input-output overhead, as well as to simplify database migration. |
The effectiveness of the index cache size depends on the nature of the calculation. For example, if you were reloading and recalculating an entire database (such as a database that is refreshed each month), a high index cache size is not helpful, because Essbase is creating blocks rather than searching the index cache for existing blocks during calculation.
Table 172 shows default and recommended settings for the index cache:
Table 172. Index Cache Size Settings
Combined size of all essn.ind files, if possible; otherwise, as large as possible. Do not set this cache size higher than the total index size, because no performance improvement results. To determine the total index size, see Index Files. |
For information about changing the I/O access mode for a database, or about changing the default for all newly created databases, see Understanding Buffered I/O and Direct I/O.
In general, if you are using direct I/O, make the index cache as large as system resources allow. If you are using buffered I/O, make the index cache as small as possible.
For information on testing and fine-tuning cache settings, see Fine-Tuning Cache Settings.