Multi-stream backup

Deployment options: Netezza Performance Server for Cloud Pak for Data System Netezza Performance Server for Cloud Pak for Data

A backup can be a multi-stream operation.

If you specify several file system locations, or if you use third-party backup tools that support multiple connections, the backup process can parallelize the work to send the data to the backup destinations. Multi-stream support can improve backup performance by reducing the time that is necessary to transfer the data to the destination.

Important: Make sure that you have information about your backup destinations. If your Netezza Performance Server database backup is stored on multiple locations or directories that are managed by different backup devices, multi-stream backups can help to improve the data transfer rates to those different destinations. If you use multiple streams, make sure that your storage device can accept multiple streams in parallel efficiently so that you can avoid situations where multiple streams might contend for a single shared resource. Consult with your backup storage administrator to determine whether multi-stream backups are appropriate for your environment.

By default, a multi-stream nzbackup process waits up to 5 minutes for all of the resources to become available to service all the requested streams. (The host.bnrStreamInitTimeoutSec registry setting specifies the amount of time for the nzbackup process to wait for resources to become active.) For example, a multi-stream backup might exceed a server-side concurrency setting that controls the number of concurrent operations that use the server. During the timeout waiting period, if concurrent jobs finish, the necessary resources might then be available for the nzbackup to proceed. If a multi-stream backup operation requests more jobs than are allowed, or if the necessary resources are not available within the timeout period, the nzbackup process exits with the following error message: Stream unresponsive after 300 seconds, operation aborted. Check concurrency limits on server.

If you use multi-stream backup to a supported third-party backup tool such as IBM® Tivoli® Storage Manager, Symantec NetBackup, or EMC NetWorker, make sure that you review the support for maximum jobs or parallelism in that tool. For more information, see the later sections that describe the support for each of these backup connectors.

Only backup operations that transfer table data support multiple destinations and streams. These operations include full and incremental backups. Other operations (for example, -noData backup, -globals backup, and the reports) use only a single destination and a single stream, even if you specify multiple destinations.

Configuring a multi-stream backup

By default, nzbackup uses one stream for each specified file system destination, or only one stream only for backups that do not specify the -dir option. If you set the host.bnrNumStreamsDefault setting to a nonzero value, you can specify a different streams default that is used for all applicable nzbackup operations. You can also specify an explicit stream count for an nzbackup command by using the -streams parameter. If you specify a nonzero stream number for the registry setting, you can use nzbackup -streams AUTO to explicitly specify that the backup must use the default one stream per file system or one stream per connector behavior.

For a description of how to set a system registry setting either temporarily or permanently, see Changing configuration settings.