Netherlands: Software

Introductie van Micorosoft SQL Server 2016

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97 C H A P T E R 5 | Broader data access max_column_id_used, uses_ansi_nulls, reject_sample_value, distribution_type, distribution_desc, sharding_col_id, remote_schema_name, and remote_object_name. Figure 5-11: Viewing metadata about external objects in SSMS. For troubleshooting the distributed execution of PolyBase, use the following DMVs: sys.dm_exec_distributed_requests Sort the rows in this DMV by total elapsed time in descending order to find the execution_id for long-running queries. Include the CROSS APPLY operator to get the text value for sql_handle from sys.dm_exec_sql_text. sys.dm_exec_distributed_request_steps Filter this DMV by the execution_id found in sys.dm_exec_distributed_requests and sort the rows by total elapsed time in descending order to find the longest-running step for a query and note its step index. You can see the execution location—Head, Compute, or data movement service (DMS), the status, and the executed command, among other details. sys.dm_exec_distributed_sql_requests Filter this DMV by the execution_id and step_index from sys.dm_exec_distributed_request_steps to view the execution progress of a SQL operation (running in the Head or Compute location). sys.dm_exec_dms_workers Filter this DMV by the execution_id and step_index from sys.dm_exec_distributed_request_steps to view the execution progress of a DMS operation (running in the DMS location). sys.dm_exec_external_work Filter this DMV by the execution_id and step_index from sys.dm_exec_distributed_request_steps to view the execution progress of a DMS operation (running in the DMS location). This DMV helps you monitor operations that consume data from an external data source. sys.dm_exec_external_operations Filter this DMV by the execution_id and step_index from sys.dm_exec_distributed_request_steps to view the execution progress of map-reduce jobs pushed down to Hadoop when a PolyBase query runs against an external table. sys.dm_exec_compute_node_errors Use this DMV to review the errors that have occurred on a compute node.

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