In default mode, solidDB^® statement execution uses only one thread per statement regardless of the complexity of statement’s search plan. If there is CPU capacity available, statement response time can be brought down by enabling statement execution to parallelize part of the effort to multiple CPU threads. If parallel execution is enabled at a time of CPU shortage, average response times stay roughly similar to default behavior. There will, however, be more variance in response times.

Parallel SQL functionality enables parallel execution for some parts of SQL statement. When an SQL statement needs a long sequential search from the database engine a new thread can be started to run the low level scan operation in parallel while the SQL interpreter processes the rows.

Parallel SQL works only with READ COMMITTED isolation level. In EXPLAIN PLAN output the keyword PARALLEL is printed even if current isolation level does not allow parallel execute.

Parallel query can be enabled or disabled by configuration parameter ParallelSQLEnabled.