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Optimizing Block Storage Caches – Data Cache

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Data Cache
Data blocks can reside on physical disk and in RAM. The amount of memory allocated for blocks in RAM is called the data cache.

Data Cache Minimum and Default Values
The minimum is 3MB and default is 3MB

Data Cache Recommended Values
As with index cache, some testing needs to be applied. However, here are a few rules of thumb for setting data cache:

  • Largest sparse aggregation * Expanded block size
  • 100 data blocks

Data Cache Considerations
Here are some circumstances under which you may want to increase your data cache setting:

Many concurrent users are accessing different data blocks. Data retrievals require that the data blocks be in memory. So the more concurrent retrievals you have accessing different blocks, the more memory you need to hold those blocks.

Calculation scripts contain functions on sparse ranges Certain calculation script functions, like @RANK and @RANGE require that all members in the range of the function and, therefore, all data blocks containing these members, be in memory.

The DLTHREADSWRITE setting (in the essbase.cfg file) is very high A larger number of parallel write threads, especially for larger block sizes, indicates the need for more data cache to hold the data blocks associated with these threads.

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