Chapter 2. NetWorker Functionality

NetWorker client-server technology uses a network Remote Procedure Call (RPC) protocol to back up data.  The NetWorker server software consists of several daemons and programs that oversee backing up and recovering, as well as storage management client configurations, an online client index, and an online media database.  NetWorker client software also includes a client-side daemon and client-side programs.

This chapter describes how NetWorker functions.  It provides a brief, simplified overview of how NetWorker performs a backup and recover.  Illustrations of backup and recovery provide a graphical overview of the storage management that NetWorker provides.  The storage management process employed with BusinesSuite Module for Informix is also illustrated.

This information may be useful for system administrators responsible for storage management and protection of the data stored in an RDBMS on a network.

How NetWorker Backs up Data

NetWorker calls on several daemons and programs when it receives a request for backup.  The daemons coordinate the tasks associated with a backup or recover and record information about what files were backed up and the media containing the backed–up data.

NetWorker Daemons and Programs

Table 2-1 provides a description of the NetWorker server daemons and programs, which contact the client for a backup and maintain the server's client index and media databases.  The online NetWorker reference pages contain further details about the NetWorker daemons and programs.

Table 2-1. NetWorker Server Daemons




Monitors an active save or recover session; agent process called by nsrd in response to a save or recover session


Monitors progress of individual save sets; agent process called by savegrp


Checks the consistency of the online file index; invoked by nsrd whenever the consistency of the online file index needs to be confirmed


Provides an RPC–based save and recover service to NetWorker clients; master NetWorker daemon


Automatically manages the server's online client index; invoked at the end of a savegrp


Provides a method for inserting entries in the online client index based on information passed by




Provides device support, to generate mount requests, and multiplex save set data during a multi-client backup—nsrd can start several nsrmmd daemons, up to the number specified in the NetWorker server's “active devices” attribute; media multiplexor daemon


Provides media and save set database management services to the local

nsrd and nsrmmd daemons and records entries in the media database; media management database daemon



Runs a group of NetWorker clients through the save process

The master NetWorker server daemon, nsrd, is responsible for several tasks:

  • starting the other server daemons

  • allocating media daemons

  • authorizing backup and recover services for the client

  • contacting clients for scheduled backups

  • maintaining NetWorker configuration information

  • monitoring backup and recover sessions

  • maintaining server statistics and message logs

The NetWorker server daemons call on the NetWorker client daemon, nsrexecd, and several client-side programs when a scheduled or on–demand backup request is received.  A temporary server agent daemon, ansrd, is started to allow the NetWorker server to monitor the progress of the backup session.  Table 2-2 provides a description of the client–side daemons and programs.

Table 2-2. NetWorker Client Daemons




Authenticates the NetWorker server's remote execution request and executes the

save and

savefs commands on the client


Browses the NetWorker server's online client index and restores the specified file to primary disk storage


Sends specified files in a multiplexed data stream to the NetWorker server for entry in the online indexes by

nsrindexd and eventual backup to media by nsrmmd



Sends information about the save sets to back up for the client; identifies save set data modified since the last level save

What Happens During a Scheduled NetWorker Backup?

When you configure a backup group on the NetWorker server, you schedule a start time for the backup group.  The nsrd server daemon starts the server's savegrp program for the backup group at the scheduled time.

The savegrp program queries the NetWorker server to determine

  • which clients configured on the server are members of the scheduled group

  • what level of save to perform

  • how many save sets to run concurrently, determined by the parallelism value set on the NetWorker server

  • when the last backup of the group occurred

If any of this information is not available on the NetWorker server, savegrp sends a request to the client-side daemon nsrexecd to run savefs on each client assigned to the backup group to gather the necessary details.

The savefs program is responsible for letting savegrp know which objects are supposed to be backed up for the client.  Once savegrp receives information about the objects to back up, savegrp assembles a work list for the server.

If problems were encountered with the online index during the last backup session, nsrd invokes the nsrck daemon to check the consistency and state of the NetWorker server's online indexes.  Then, nsrd starts the online file index insertion daemon, nsrindexd.

The savegrp program contacts the first client on the server's work list.  The client's nsrexecd daemon is invoked and starts a save session of the first save set listed on the server's work list.  The save program passes to nsrd all save criteria, such as group, client, save sets, and level of the save data.  With this information, nsrd determines the pool of volumes that store the data and forwards the information to the media daemon.

The media daemon, nsrmmd

  • sends a message to the console of the NetWorker server, requesting a mount of the media assigned to the volume pool indicated by nsrd

  • writes the data sent by save to storage media

  • forwards storage information to nsrmmdbd for recording in the NetWorker server's online media database

Anytime there is a lull in save set activity from the client, the NetWorker server attempts to find another save set in the group to keep the process moving along.  The savegrp program attempts to concurrently back up as many save sets as possible, up to the limit set by the parallelism attribute in the NetWorker server's configuration, so as to use the backup devices to their maximum potential.

The savegrp program repeats the process for each item on the server's work list until all clients in the group are backed up.  Before the savegrp completes, nsrim is invoked and the NetWorker server's bootstrap save set is backed up.  The final results of the savegrp execution are sent back to the server and are included in the “savegroup completion” notification that NetWorker e-mails to root.  (Refer to Chapter 7, “Customizing NetWorker Backups,” in the IRIX NetWorker Administrator's Guide for details on using and customizing NetWorker notifications.)

Note: For BusinesSuite Module for Informix, the “savegroup completion” notification is produced for dbobject backups only— for information on logical log backups, use the nsrinfo command, or query the bar_action and bar_object tables for information on the backup and restore activities for OnLine Dynamic Server dbobjects.

Refer to the IRIX NetWorker Administrator's Guide or the nsrinfo(1M) reference page for help on using nsrinfo.  Refer to Chapter 4, “Catalog Tables,” in the INFORMIX-Online Dynamic Server Backup and Restore Guide provided with your OnLine Dynamic Server software for information about ON-Bar catalog tables.

Figure 2-1 shows a flowchart of NetWorker client and server daemons and programs during a scheduled save.

Figure 2-1. NetWorker Daemons During Scheduled Save

Figure 2-1 NetWorker Daemons During Scheduled Save

This is how NetWorker daemon processes and programs interact during a scheduled save.  Heavy lines represent movement of data from local disk to storage medium.

How NetWorker Recovers Data

When NetWorker receives a recover request from a client, the server's nsrd daemon contacts the server's media daemon, nsrmmd.  This daemon contacts the server's media database daemon, nsrmmdbd, to determine which media contain the save set requested by the recover command.  Once it obtains the save set's media location, nsrmmd issues a mount request, the media is positioned at the beginning of the save set, and the save set stored on the mounted media is passed to nsrmmd.  The media daemon forwards the save set to the client's recover program, which restores data to the client's filesystem.

Figure 2-2 shows a flowchart of NetWorker server and client daemons and programs during recovery of NetWorker client data.

Figure 2-2. NetWorker Daemons During Recover Session

Figure 2-2 NetWorker Daemons During Recover Session

This is how NetWorker daemon processes and programs interact during a recover session.  Heavy lines represent movement of data from storage medium to local disk.

How BusinesSuite Module for Informix Connects NetWorker to ON-Bar

NetWorker and BusinesSuite Module for Informix provide storage management services for OnLine Dynamic Server dbobjects through an X-Open® backup services (XBSA) connection to ON-Bar.  BusinesSuite Module for Informix provides the services that connect NetWorker functionality to ON-Bar.  You use the NetWorker administration program to set up backup schedules, label backup volumes, and configure the system running OnLine Dynamic Server as a storage management client of the NetWorker server.

When nsrd triggers a scheduled backup for an OnLine Dynamic Server instance on the NetWorker server, savegrp executes the nsrdbmi script instead of performing a standard save.  The nsrdbmi script invokes ON-Bar, which interacts with NetWorker through the XBSA API to coordinate a backup of the specified OnLine Dynamic Server dbobjects.

Once the scheduled backup completes, ON-Bar performs a backup of the logical logs associated with the saved ON-Bar dbobjects, closes and backs up the current logical log, and opens a new log.  Then NetWorker performs a “full” backup of the OnLine Dynamic Server instance's emergency boot file and server configuration file.  Finally, NetWorker copies the server's bootstrap save set to tape, and e-mails a “savegroup completion” notification.

NetWorker takes care of the scheduling and storage management tasks, while ON-Bar takes care of passing the data from OnLine Dynamic Server to NetWorker.

Figure 2-3 shows the functional relationship between NetWorker, BusinesSuite Module for Informix, ON-Bar, and OnLine Dynamic Server during backup.  NetWorker connects to ON-Bar through an XBSA API to provide scheduled backups.  Heavy lines represent movement of data from local disk to storage medium.

Figure 2-3. NetWorker Connection to ON-Bar

Figure 2-3 NetWorker Connection to ON-Bar

The OnLine Dynamic Server software can exist on the same system as the NetWorker server software, or it can exist on a separate system.  Since nsrdbmi substitutes for the client-side program save during a backup, the BusinesSuite Module for Informix software must be installed on the system where you installed OnLine Dynamic Server.  No matter where the system running OnLine Dynamic Server resides, the system is considered a storage management client of the NetWorker server.

When an ON-Bar restore request is initiated, the NetWorker XBSA API translates the object names requested by ON-Bar into a format understood by NetWorker and forwards it to the NetWorker server's nsrd daemon.  The media daemon, nsrmmd, searches the NetWorker server's online media database for the media containing the requested objects and recovers the data to the OnLine Dynamic Server as described in “How NetWorker Recovers Data”.

Figure 2-4 shows the functional relationship between NetWorker, BusinesSuite Module for Informix, ON-Bar, and OnLine Dynamic Server during restore.

Figure 2-4. Restore Initiated by ON-Bar

Figure 2-4 Restore Initiated by ON-Bar

This shows data movement during a restore initiated by ON-Bar.  Heavy lines represent movement of data from storage medium to local disk.

Chapter 3 provides instructions for configuring OnLine Dynamic Server as a NetWorker client for scheduled backups.