| 17 | | * NumberOfBuffers: |
| 18 | | |
| 19 | | This controls the amount of RAM used by Virtuoso to cache database files. This has a critical performance impact and thus the value should be fairly high for large databases. Exceeding physical memory in this setting will have a significant negative impact. For a database-only server about 65% of available RAM could be configured for database buffers. |
| 20 | | Each buffer caches one 8K page of data and occupies approximately 8700 bytes of memory. |
| 21 | | |
| 22 | | In order to avoid out of memory error, you should make sure the values for the paramaters NumberOfBuffers and MaxCheckpointRemap are not set with the same values. Changing the value of the parameter MaxCheckpointRemap with let's say 1/4 of the DB size will resolve the issue. |
| 23 | | |
| 24 | | * AsyncQueueMaxThreads: control the size of a pool of extra threads that can be used for query parallelization. This should be set to either 1.5 * the number of cores or 1.5 * the number of core threads; see which works better. |
| 25 | | |
| 26 | | * ThreadsPerQuery: the maximum number of threads a single query will take. This should be set to either the number of cores or the number of core threads; see which works better. |
| 27 | | |
| 28 | | * IndexTreeMaps: the number of mutexes over which control for buffering an index tree is split. This can generally be left at default (256 in normal operation; valid settings are powers of 2 from 2 to 1024), but setting to 64, 128, or 512 may be beneficial.A low number will lead to frequent contention; upwards of 64 will have little contention. |
| 29 | | |
| 30 | | * Set ThreadCleanupInterval and ResourcesCleanupInterval to 1 in order to reduce memory leaking. |
