Understanding Essbase Caches
Essbase uses five memory caches to coordinate memory usage:
Table 171. List of Essbase Caches
Cache | Description |
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Index cache | A buffer in memory that holds index pages. How many index pages are in memory simultaneously depends upon the amount of memory allocated to the cache. |
Data file cache | A buffer in memory that holds compressed data files (.pag files). Essbase allocates memory to the data file cache during data load, calculation, and retrieval operations, as needed. The data file cache is used only when direct I/O is in effect. |
Data cache | A buffer in memory that holds uncompressed data blocks. Essbase allocates memory to the data cache during data load, calculation, and retrieval operations, as needed. |
Calculator cache | A buffer in memory that Essbase uses to create and track data blocks during calculation operations. |
Dynamic calculator cache | A buffer in memory that Essbase uses to store all of the blocks needed for a calculation of a Dynamic Calc member in a dense dimension (for example, for a query). |
Essbase provides default size settings for each cache; you can adjust the sizes as needed for each database. Appropriate cache size is affected by many factors, including database size, block size, index size, and available server memory. Cache size settings can significantly affect database and general server performance.
The following topics provide information about sizing caches for performance.