While the data cache holds data blocks, the data file cache holds data files (PAG files) in memory—if you are using Direct I/O. If you are not using Direct I/O, the data file cache is not used at all. Under Direct I/O, how much of the data within data files can fit into memory at one time depends on the amount of memory that you allocate to the data file cache.
Data File Cache Minimum and Default Values
The minimum 10MB and default 32MB
Data File Cache Recommended Values
- Use the combined size of all ESSn.PAG files, if possible; as large as possibleotherwise, up to 2 GB.
- In general, if deciding whether to allocate memory to the data cache or to the data filecache, give priority to the data file cache (if you are using Direct I/O).
Cache Memory Locking
When enabled, cache memory locking gives Essbase exclusive use of the memory specified for the index, data, and data file caches. It is available only if you use Direct I/O.
If you enable this feature, you may improve performance because the system memory manager does not need to swap and reserve space for the memory that database caches use. Cache memory locking gives the Essbase kernel priority use of system RAM.
The sizes you enter for the Essbase caches normally represent maximum values, which may or may not be attained during a calculation. However, the cache memory locking feature effectively allocates and locks the entire amount of cache memory exclusively for Essbase.
Depending on other applications running on the server at the same time, the maximum amount of memory specified might not be available, and performance could be degraded significantly. Therefore, if you enable this feature, leave at least one-third of the system RAM available for non–Essbase use.
Cache memory locking is disabled by default.