Outline structure and application design determine whether enabling parallel calculation can improve calculation performance. Before you enable parallel calculation, review the following guidelines, which will help you get the full benefit of parallel calculation:
Use the uncommitted access isolation level. Parallel calculation is not supported if you use the committed access isolation level. See Uncommitted Access.
One or more formulas present in a calculation may prevent Essbase from using parallel calculation even if it is enabled. For a description of formulas that may force serial calculation regardless of parallel calculation settings, see Formula Limitations.
Calculation tasks are generated along the last n sparse dimensions of an outline. These sparse dimensions used to identify tasks are called task dimensions. The number of task dimensions, n, is either selected dynamically by Essbase, or you can override the number by specifying a value for CALCTASKDIMS in the essbase.cfg file.
Order the sparse dimensions in an outline from smallest to largest, based on actual size of the dimension (as reported by the MaxL statement query database DBSNAME get dbstats dimension). This ordering recommendation is consistent with recommendations for optimizing calculator cache size and consistent with other outline recommendations. For a description of situations that may need to use additional dimensions (more than the last sparse dimension) and for instructions on how to increase the number of sparse dimensions used, see Identifying Additional Tasks for Parallel Calculation.
Parallel calculation is effective on nonpartitioned applications and these partitioned applications:
Transparent partitions if the calculation occurs at the target database. The number of sparse dimensions specified by CALCTASKDIMS in the essbase.cfg file or by SET CALCTASKDIMS in a calculation script must be set at 1 (the default value). For information on limitations imposed by the use of parallel calculation with transparent partitions, see Transparent Partition Limitations; for information on using CALCTASKDIMS or SET CALCTASKDIMS, see Identifying Additional Tasks for Parallel Calculation.
If you have selected incremental restructuring for a database and have made outline changes that are pending a restructure, do not use parallel calculation. Unpredictable results may occur.
Update transactions, such as calculations and data updates, are more resource-consuming requests than MDX queries or report scripts. When a storage device is fast, Essbase allows more parallel calculation threads to get reasonable throughput; when a storage device is slower, Essbase may need to have a smaller number of parallel calculation or other update threads. You can use the Essbase.cfg setting MAXACTIVEUPDATETRANSACTIONS to control the number of update transactions. For more information, see the topic for MAXACTIVEUPDATETRANSACTIONS in the Oracle Essbase Technical Reference.