Best Practices
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Using a Host/Client Group for Guarding Teradata Devices in a Clique
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Best Practice for Preparation for Initial Data Transformation or Rekey
Using a of Host/Client Group to Guard Metadata Directories
Thales recommends that customers use a host group exclusively for guarding and management of the CTE external metadata directories across all nodes in Teradata cluster. (For details about the CTE metadata directory, see Location of the CTE Private Region.)
By using a Host/Client Group, you can apply the same policy to the external metadata directory (/var/opt/teradata/vormetric/vte-metadata-dir) on all of the CTE protected nodes in the cluster.
Using a Host/Client Group for Guarding Teradata Devices in a Clique
Thales recommend that customers use a Host/Client Group to guard and manage the devices shared by all CTE protected nodes in a clique. Each clique in the cluster should be associated with a separate Host/Client Group. When configuring the Host/Client Group, the members for that client group are the nodes that belong within a clique in the cluster.
Example 1: If you have a cluster consisting of 4 cliques where there are 2 nodes sharing disks in each clique, you would create 4 Host/Client Groups, one for each clique. In each Host/Client Group, you would add the 2 nodes that are associated with the clique.
Example 2: If you have a cluster consisting of 1 clique where there are 6 nodes sharing disks in the clique, you want to create 1 client group with all 6 members that belong within that clique.
Below is an example of the Host Groups for a cluster consisting of three cliques and one metadata group:
Best Practice for Preparation for Initial Data Transformation or Rekey
With large amounts of data managed in Teradata clusters, duration of initial data transformation and/or subsequent rekey can be very long and challenging because the database must be stopped during the data transformation process. Although you cannot transform data without shutting down the database, you may be able to reduce the transformation time by distributing the transformation of the guarded devices across multiple nodes in your cluster.
Because multiple nodes in a cluster within a clique share access to the same devices, you can designate a subset of devices to each node within the clique for initial data transformation or subsequent rekey. This requires unguarding all of the IDT-Capable devices in the Host/Client Group associated with the clique, and re-enabling each IDT-Capable GuardPoint on the node designated for the data transformation of that IDT-Capable GuardPoint. The device then remains unguarded on other nodes until the data transformation completes.
After the data transformation completes, you can then enable the guarded devices at the Host/Client Group level. Enabling the guarded device at Host/Client Group level enables the guarded devices on all of the nodes within the clique to share access to the device.
After transforming data and guarding each device on all of the nodes, you can then restart the database.
As described in Interoperability with Host Groups, the metadata file for each device is replicated to the hosts in the cluster that share access to the device. As noted, replication of metadata files is automatic.
