On what basis child jobs are created?

[smith_jones]

Hi,

We schedule backups and enable the multiple data streams option. 

If we specify three NEW_STREAMS in the backup selection attribute of the policy we will get three child jobs and one master job.

But in some policies we do not specify any NEW_STREAM but multiple data streams is enabled. Then on what basis the child jobs are made\streamed by default of a policy. In some we will see 3 child jobs and in some 4 child jobs. On what basis these are created by netbackup?

Best exmaple Hotcatalog backup. It automatically creates 3 child jobs.  Though multiple data streams is not enabled by default.

Like this some policies create their own. On what basis?

[Marianne]

Catalog backup is a different subject - 3 child jobs will always be created because of the different tasks performed as part of a catalog backup. 
See https://www-secure.symantec.com/connect/forums/about-catalog-backup#comment-10387581  

Standard or MS-Windows can ONLY generate multiple child jobs if 'Allow Multiple Data Streams' is selected in Attributes.

Having this setting enabled will have the exact same results with the following 2 examples:

Example 1:

NEW_STREAM
C:\
NEW_STREAM
D:\
NEW_STREAM
E:\

Example 2:

C:\
D:\
E:\

As you can see - NEW_STREAM in example 1 was not necessary.

I only use NEW_STREAM when I want to group multiple entries into a single stream, e.g.

NEW_STREAM
C:\
D:\
NEW_STREAM
E:\folder1
E:\folder2
NEW_STREAM
E:\folder3
E:\folder4

(I believe all of this is explained in NBU Admin Guide 1)

Child streams for a database agent policy is dictated by parameters in the backup script and amount of data files.

Hope this helps.

[Andy_Welburn · Accepted solution]

From the context sensitive help in the Policy Attributes tab:

The Allow multiple data streams attribute specifies that NetBackup can divide automatic backups for each client into multiple jobs. The directives, scripts, or templates in the backup selection list specify whether each job can back up only a part of the backup selection list. Since the jobs are in separate data streams, they can occur concurrently.

• The directives, scripts, or templates in the backup selection list determine the number of streams (backup jobs) that start for each client. The list also determines how the backup selection list is divided into separate streams.

• The following settings determine the number of streams that can run concurrently:

   • Number of available storage units
   • Multiplexing settings
   • Maximum jobs parameters

Multistreamed jobs consist of a parent job to perform stream discovery, and children jobs for each stream. In the Activity Monitor, the children jobs display the Job ID of the parent job. Parent jobs display a dash (-) in the Schedule column.

So, the parent job will 'determine' the number of child jobs depending upon what it finds on the client with respect to the policy's backup selection list.

e.g. (with multiple data streams selected in a policy) a backup selection of:

ALL_LOCAL_DRIVES - number of streams would be determined by number of drives (+ system state) or filesystems on client

C:\SOMEFOLDER\* - number of streams would be determined by the number of folders/files directly within the SOMEFOLDER folder

C:\SOMEFOLDER or C:\SOMEFOLDER\ - number of streams determined by backup selection itself i.e. 1

C:\SOMEFOLDER\A and C:\SOMEFOLDER\B - again, number of streams determined by backup selection itself i.e. 2

Hopefully you get the idea - stream discovery by the parent essentially determines the number of streams as a consequence of what it 'discovers' on the client

Catalog Backup is a different matter as Marianne has already mentioned.