User Guide > Configuring the TDV Massively Parallel Processing Engine > Setting Up and Configuring the TDV MPP Engine
 
Setting Up and Configuring the TDV MPP Engine
The TDV MPP Engine is enabled by default. It is recommended to use the Active Cluster deployment strategy for harnessing the power of MPP Engine.
An Active Cluster configuration is not necessary, but can provide optimal performance for parallel query processing.
To set up and configure the TDV MPP engine
1. Open Studio.
2. From the Administration menu, choose Configuration.
3. Navigate to Server > SQL Engine > Parallel Processing.
Configuration Parameter
Description
Maximum Heap Memory
Maximum heap memory allocated for parallel processing. For this value to take effect you will need to disable and enable parallel processing. Default value will be 10% to total system memory, and the value set must be greater than 0.
Enabled
Determines whether the MPP engine is enabled or not. The default value is true for Linux environments and False for Windows and AIX environments.
Limit scalar subqueries
True or False
Controls whether you want a LIMIT 1 clause to automatically append to your scalar subqueries.
Logging Level
Set to one of: OFF, LOW, MEDIUM, HIGH
LOW level allows for distributed query routing to be traced - from original TDV query to Drill query to partitioned TDV virtual scan queries. Fallback reason is also recorded. MEDIUM level augments this information with resource allocation information pertaining to each query. HIGH level further augments this information with a non-parallelization reason.
Maximum Direct Memory
Maximum direct memory allocated for parallel processing. For this value to take effect you will need to disable and enable parallel processing. Default value will be 50% to total system memory, and the value set must be greater than 0.
Minimum Partition Volume
The minimum data volume to be fetched by each partition (in MB). This setting is approximate, because it is based on virtual scan query result volume estimates.
Default value is 256. If set to 0 or a negative value, it has no effect.
Resource Quota per Request
This value is the percentage of system resources that each request is limited to during parallel execution.
Setting this value to 100 would allow only 1 query at a time to run in the MPP Engine, using a value of 50 would allow 2 concurrent queries to be served by the MPP Engine and so on and so forth.
Startup Connection Retry Count: 30
This value is the number of times the server will try to autoconfigure the parallel runtime engine at server startup.
Default value is 30.
Startup Connection Retry Interval
This value is the amount of time in milliseconds the server will wait before retrying to auto-configure the parallel runtime engine at server startup.
Default value is 1000.
4. Click Apply.
5. Click OK.
6. Open the data source editor for the data sources involved in MPP.
7. Open the Advanced tab, locate the Concurrent Request Limit field and adjust the value according to the instruction given below.
Configuration Parameter
Description
Concurrent Request Limit
This configuration can take a value between 0 to 65536. It specifies the concurrency limits to be imposed on the underlying data source. If concurrentRequestLimit is set to 0, then partitioned queries will not be issued against the data source and the query engine will not operate in parallel mode against the data source. For any value greater than 0, the query engine will throttle concurrency to X number of concurrent connections, where concurrentRequestLimit=X. Choose concurrentRequestLimit appropriately by taking into account the acceptable concurrent load on the data source as well as the number of concurrent queries in DV that will run in parallel (determined by "Request Quota Per Request").
For supported data sources, you can use TDV Studio to find the property specified by the adapter and assign its value. Follow these steps to assign a value to the Concurrent Request Limit:
1. Right Click and open the data source
2. Open the Overrides tab.
3. In the “Simple Properties”, type ConcurrentRequestLimit in the Search Text box.
4. Choose the property and assign a valid value.