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| Oracle7 Enterprise Backup Utility Administrator's Guide | Library |
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Topics covered in this chapter are:
Once you register database identification information with the Enterprise Backup Utility, the utility automatically locates the tablespaces, datafiles, control file(s), and archived log files associated with the database for all future backup and restore operations.
EBU maintains the configuration information on target databases in a catalog on a separate Oracle7 Server. When you are ready to perform a backup or restore, the utility retrieves the physical details about the database structure from the backup catalog.
After restoring a database, you must apply other recovery steps to bring the database to a consistent point-in-time prior to the point of failure or damage.
Note: Restoring is only necessary after media failure. If you are performing instance recovery, you need not restore the database files. The Oracle7 Server reads the online redo log files and automatically performs instance recovery.
During restores, EBU automatically uses the most recent backup available for each file, minimizing the amount of recovery that is necessary. Data can also be restored in parallel from multiple devices to facilitate speedy restoration.
Upon restore, the utility checks data block addresses to ensure there are no gaps, verifies that data block numbers correspond to actual datafiles, and performs a checksum on each file (if checksumming was enabled during backup).
Figure 1 - 1. Component Layers in the Enterprise Backup Utility
Target Databases
Target databases are the Oracle7 databases designated for backup. You identify target databases to the Enterprise Backup Utility using the register command.
Backup Catalog Database
The tables comprising the backup catalog are stored in the backup catalog database. The backup catalog database is an Oracle7 database separate from any of the target databases. Its sole purpose is to host the backup catalog.
The suggested size of the backup catalog database is about 20 MB.
Attention: Oracle Corporation strongly recommends that the backup catalog database be dedicated exclusively to storing the backup catalog, and that it run on a separate machine from all target databases.
Backup Catalog
The backup catalog is a collection of tables in an Oracle7 database. It contains structural information about the target databases, as well as a backup and restore history for each target database (including the archived redo logs affiliated with each backup job).
Command Scripts
The DBA or system administrator creates command scripts to define and invoke backup and restore operations. Each command script specifies the operation to be performed and accesses the components needed to carry out the operation.
Control Process
The control process oversees the overall backup/restore operation. It takes the command scripts and retrieves and stores catalog information. It also spawns I/O processes.
I/O Processes
I/O processes read and write database files between storage disks and the backup media devices.
Database Module for Oracle (API Glue)
The Enterprise Backup Utility works in conjunction with a third-party media management product to provide complete backups and restores of the target databases.
The interface from EBU to the media management product is provided by the Database Module for Oracle (DMO). It is a set of routines that allows the reading and writing of data to the media device.
Note: You must obtain the DMO from your media management vendor before using the Enterprise Backup Utility.
Media Management Product
The media management product handles the direct interaction with the media devices and provides such features as scheduling, data compression, media aging reports, labeling, and network backups.
Media Device
The media management product uses media devices to store database files. Common media devices are 4-mm tapes, 8-mm tapes, Digital Linear Tapes, and library CDs.
Figure 1 - 2. Architecture of the Enterprise Backup Utility
obackup
Monitors all other process and communicates with the target database and the backup catalog. The obackup process spawns the Instance Manager if one is not already running
brio
Coordinates between obackup and the brdk and brtp processes: one brio process is spawned per parallel I/O stream
brdk
Handles read/write of disk files. By default, there is one brdk per I/O stream, per file. If the mux specifier is used, multiple brdk processes are created for single I/O streams.
brtp
Handles read/write of tape files. There is one brtp process per parallel I/O stream.
brd (Instance Manager)
Daemon process that monitors the backup catalog and obackup process. The Instance Manager handles cleanup for all backup and restore operations which terminate abnormally.
Figure 1 - 2 illustrates only a single database being backed up or restored onto one media device. On any given host, the Enterprise Backup Utility executables must be installed on a one-per-oracle software owner basis. Figure 1 - 3 illustrates a single obackup control process with two spawned I/O processes, streaming to two media devices.
Figure 1 - 3. Single obackup Instance with Two Parallel Data Streams
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