Netherlands: Software

Introductie van Micorosoft SQL Server 2016

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91 C H A P T E R 5 | Broader data access sys.dm_exec_compute_nodes Returns the following columns: compute_node_id, type (HEAD or COMPUTE), name (server name and port number), and address (IP address). sys.dm_exec_compute_node_status Returns the status of all nodes in the group in the following columns: compute_node_id, process_id, process_name (Engine or DMS), allocated_memory, available_memory, process_cpu_usage, total_cpu_usage, and thread_count. sys.dm_exec_dms_services Reports the current status of the DMS service on each compute node. Creating PolyBase data objects To query data sources in Hadoop or blob storage, you need to create a set of T-SQL objects. First, if you are connecting to a Kerberos-secured Hadoop cluster or to blob storage, you need to create a database-scoped credential. Next, you need to create an external data source to define the location of your data and an external file format to describe the structure of your data. Then you can create external tables to define the table columns and associate the external table with an external data source and external file format. Database-scoped credential If you have data stored in blob storage or a Hadoop cluster that is configured to use Kerberos authentication, you must provide authentication information so that PolyBase can securely connect to the data source. To do this, you must create a master key and a database-scoped credential. The master key encrypts the database-scoped credential. When you create a database-scoped credential for blob storage, as shown in Example 5-29, replace the placeholder token for PASSWORD with a strong password, provide a unique name for the credential, and replace the placeholder token for SECRET with the storage account key for blob storage. To get this key, go to the storage account blade in the Azure Management Portal, click the Settings button, and then click Access Keys in the Settings blade. Click the Copy button to the right of one of the keys to store the key on the clipboard. Example 5-29: Creating a database-scoped credential for blob storage -- Create a master key if one does not already exist CREATE MASTER KEY ENCRYPTION BY PASSWORD = ''; -- Create a database-scoped credential CREATE DATABASE SCOPED CREDENTIAL AzureBlobStorageCredential WITH IDENTITY = 'user', SECRET = ''; Note You can use any string for IDENTITY when creating a database-scoped credential for blob storage. Authentication requires only the storage account key. If you are connecting to a Kerberos-enabled Hadoop cluster, create the master key and database- scoped credential as shown in Example 5-30. Replace the placeholder token for PASSWORD with a strong password, provide a unique name for the credential, and replace the IDENTITY and SECRET placeholder tokens with the Kerberos user name and password, respectively.

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