Hana - Parallel Query

Sap Hana Architecture

Thread pools Configuration

Two thread pools control the parallelism of statement execution.

  • SQLExecutors: Front End SQL receiver, execute OLTP query, delegate OLAP query to Job executor
  • and JobExecutors: Execute parallel, complex OLAP query


  • Handle incoming request
  • Execute Simple Statement (OLTP)
  • Delegate Complex Query to the JobExecutor pool


  • Execute Complex Statement as parallelized job
  • Assign Jobs to available thread


SQL Executor: indexserver.ini.

  • sql_executors - min target number of threads that can be busy(default # of available thread)
  • max_sql_executors - max number of threads that can be busy. Not set by default so that new threads are created to handle incoming requests.

Parameters for JobExecutor

JobExecutor: global.ini or indexserver.ini.

  • max_concurrency - max target number of threads that can be busy. Note that from SPS12, this parameter should only need to be modified for multitenant database container installations.
  • max_concurrency_hint - Limit concurrency hint even if more active job workers would be available.
  • default_statement_concurrency_limit - Used to restrict the actual degree of parallel execution per connection within a statement.

Hana Max Concurrency


Parallelism Stopen HINT Details - MAX_CONCURRENCY Controls concurrency. This setting only accepts the value 1 (single thread plan execution) and the Join Engine determines suitable parallelism by default.





SAP auto-determines degree of parallelism statement execution with max parallelization.

Degree of Parallelism:

  • default: best effort: unlimited use of threads for parallel statement execution
  • can be controlled by statement thread limit per statement in workload classes.
  • default_statement_concurrency_limit (global.ini)

8 means max 8 threads can be engaged at any one time for any one statement.

Hana Default Statement Conc Limit

Execution Priority

Job Executor parameter that set the execution priority for a connection (ie for a statement)

alter user SYSTEM set parameter PRIORITY = '9';
select priority from m_connections where connection_id = CURRENT_CONNECTION;

Workload Class

workload class permits to limit also the parallelism.

Documentation / Reference

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