General Error: NetBackup NDMP multiplexed backup fails with Status 20, invalid command parameter.

Article:TECH148186  |  Created: 2011-01-14  |  Updated: 2011-01-18  |  Article URL
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Technical Solution




A multiplex NDMP backup fails with Status Code 20, invalid command parameter.

NetBackup bpbrm reports: multiplexing with NDMP not supported.



14:28:17.250 [3528.3424] <16> bpbrm main: multiplexing with NDMP not supported
14:28:18.546 [3528.3424] <2> bpbrm Exit: ERROR 20 sent to parent process 



NetBackup 7.0.1. Master Server with a NetBackup 6.5.4 Media Server.

NetBackup 7.0.1 release notes:

Remote NDMP multiplexing enables concurrent writing of multiple backup streams, through a NetBackup media server, to a single tape drive. The main reason for multiplexing is to improve overall NetBackup performance by better using tape drives.

State of the art tape drives can typically stream data much faster than NDMP hosts can create provide backup data. That is especially true with small file sizes.

Multiplexing addresses the following:

* It allows for a greater number of concurrent backup operations given a limited number of target tape drives. Because the tape drives can accept data faster than an NDMP host can provide data, several NDMP hosts (or NetBackup clients) can concurrently send data to the same tape drive. That reduces the overall backup time.

* Many tape drives require a high minimum data rate to maintain streaming. When data is not streamed fast enough, the drive must reposition and that reduces the efficiency of the tape device. It also lengthens the backup time and subjects the tape drive to increased wear.


The error, multiplexing with NDMP not supported was generated from the 6.5.4 Media Server.

The new NDMP multiplexing feature only applies to 7.0.1 media servers.


  1. Check the NDMP policy and if using a 6.5.4 Media Manager Storage unit ensure that the policy schedule has Media multiplexing set to 1.
  2. Perform remote NDMP multiplex backups with 7.0.1 Media Manager Storage Units.
  3. Upgrade 6.5.x media servers to 7.0.1 to take full advantage of this feature.

Note: The remote NDMP multiplexing feature does not apply to NDMP Storage Units.

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