Chapter 2. NetWorker Functionality

This chapter is for readers who are interested in the “behind the scenes” operation of NetWorker and the BusinesSuite Module for Oracle. The information in this chapter may be useful for system administrators responsible for storage management and protection of the data stored in an Oracle7 RDBMS on a network. If you are not interested in the detailed underpinnings of the product, please proceed directly to Chapter 3, “Configuring the Software.”

NetWorker client-server technology uses a network Remote Procedure Call (RPC) protocol to back up your data. The NetWorker server software consists of several daemons and programs. They oversee the backup and recover processes, the storage management client configurations, an online client index, and an online media database. The NetWorker client software includes a client-side daemon and user programs.

This chapter provides a brief, simplified overview of how NetWorker performs a backup and recover. Illustrations of the backup and recover processes provide a graphical overview of the storage management process employed by NetWorker. The storage management process employed by BusinesSuite Module for Oracle is also illustrated.

NetWorker Backup Facility

NetWorker calls upon several daemons and programs when it receives a backup request. The daemons coordinate the tasks associated with a backup or recover. They also record information about what was backed up and 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 file index and media databases. The NetWorker reference pages contain further details about the NetWorker daemons and programs.

Table 2-1. NetWorker Server Daemons and Programs




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


Monitors the progress of individual save sets; agent process invoked 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, generates mount requests, and multiplexes 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 daemons 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 upon the NetWorker client daemon, nsrexecd, and several client-side programs when they receive a scheduled or on–demand backup request. 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 and Programs




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 Scheduled 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 client resources configured on the NetWorker server to determine

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

  • 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 then 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 will 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, to maximize the potential of all backup devices.

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 is backed up. The final results of the savegrp execution are sent back to the server and are included in the savegroup completion report, which is sent through e-mail to root.

Refer to the chapter “Customizing NetWorker Backups,” in the IRIX NetWorker Administrator's Guide for details on using and customizing NetWorker notifications.

Note: For BusinesSuite Module for Oracle, the savegroup completion report contains only the final Enterprise Backup Utility completion status. Detailed information about backup or restore operations is contained in the Enterprise Backup Utility log file.

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

Figure 2-1. NetWorker Scheduled Backup Processes

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.

NetWorker Recover Facility

When NetWorker receives a recover request from a client, the server's nsrd daemon contacts the server's media daemon, nsrmmd. The nsrmmd daemon contacts the server's media database daemon, nsrmmdbd, to determine which media contain the save set requested by recover. Once the save set's media location is obtained, nsrmmd issues a mount request, the media is positioned to 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 Recover Processes

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 NetWorker Connects to Enterprise Backup Utility

NetWorker and BusinesSuite Module for Oracle provide storage management services for Oracle7 Server data (such as tablespaces, archived logs, parameter files, and so on) through the Oracle Tape Backup API. BusinesSuite Module for Oracle provides the services that connect NetWorker functionality to the Enterprise Backup Utility. You use the NetWorker administration program to set up backup schedules, label backup volumes, and configure the system running Oracle7 Server as a storage management client of the NetWorker server.

When a scheduled backup for an Oracle instance is triggered by nsrd on the NetWorker server, savegrp executes the nsrdmo script instead of performing a standard save. The nsrdmo script invokes the Enterprise Backup Utility process obackup, which interacts with NetWorker through the Oracle Tape Backup API to coordinate a backup of the Oracle7 Server database files. Next, client and media indexes are saved, the NetWorker server's bootstrap file is backed up, and a savegroup completion notification is sent.

NetWorker takes care of the scheduling and storage management tasks, while the Enterprise Backup Utility takes care of passing the data from Oracle to NetWorker.

Figure 2-3 shows the functional relationship between NetWorker, BusinesSuite Module for Oracle, Enterprise Backup Utility, and Oracle7 Server during a scheduled backup.  Heavy lines represent movement of data from local disk to storage medium.

Figure 2-3. Enterprise Backup Utility and NetWorker Backup

The Oracle7 Server software can exist on the same system as the NetWorker server software or it can exist on a separate system. Since nsrdmo substitutes for the client-side program save during a backup, the BusinesSuite Module for Oracle software must be installed on the system where you installed Oracle7 Server. No matter where the system running BusinesSuite Module for Oracle and Oracle7 Server resides, the system is considered a storage management client of the NetWorker server.

When an Enterprise Backup Utility restore request is initiated, the BusinesSuite Module for Oracle translates the object names requested by Enterprise Backup Utility 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 object(s) requested and recovers the data to the Oracle7 Server as described in the section “NetWorker Recover Facility”.

Figure 2-4 shows how data moves from the NetWorker server to Oracle7 Server during an Enterprise Backup Utility restore session.

Figure 2-4. Enterprise Backup Utility and NetWorker Restore

This shows data movement during a restore initiated by the Enterprise Backup Utility. Heavy lines represent movement of data from storage medium to local disk.