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Features and Architecture


This chapter describes the main features and components of the Enterprise Backup Utility, and briefly discusses the system architecture.

Topics covered in this chapter are:

Introduction

An Oracle database consists of datafiles, control files, parameter files, log files, and archived log files (when using log archiving). The Enterprise Backup Utility provides an effective mechanism to back up, restore, and recover all types of Oracle7 database files. EBU only supports Oracle7 Databases.

Enterprise Backup Utility automatically locates the tablespaces, datafiles, control file(s), and archived log files associated with the database for all 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 EBU Catalog.

Database Restore vs. Database Recovery

A database restore is an essential part of database recovery, but not synonymous with it. Database recovery allows you to reconstruct a damaged database and return it to a consistent state that it had prior to damage. Restoring is the processing of rebuilding corrupted or lost files from backup copies.

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.:  

Performance

Multiple datafiles or tablespaces can be backed up simultaneously to multiple devices in parallel. This fast, parallelized backup reduces the time required to perform backups.

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.

Error Checking

EBU performs block header validation each time it is invoked to make a backup of a datafile. These checks are performed automatically for all tablespaces and datafiles for the database being backed up. Optionally, EBU can perform per-file checksums of a file's contents.

When performing backups, the Enterprise Backup Utility checks for any inconsistency in the configuration of the database and, if online, updates the EBU Catalog if the configuration information does not match.

Upon restore, the utility checks data block headers 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).

Report Generation and Job Administration

The Enterprise Backup Utility includes a EBU Catalog management utility, ebutool, that allows you to generate reports on information on target databases and their corresponding backup and restore operations. It also administrates EBU jobs.

Enterprise Backup Utility Architecture

Component Layers

Figure 1-1, "Component Layers in the Enterprise Backup Utility" illustrates the component layers in Enterprise Backup Utility architecture.

Figure 1-1 Component Layers in the Enterprise Backup Utility

Table 1-1 Component Layers in the Enterprise Backup Utility

Component   Description  

Target Databases

 

Target databases are the Oracle7 databases designated for backup. You identify target databases to the Enterprise Backup Utility using the register command.

 

EBU Catalog Database

 

The tables comprising the EBU Catalog are stored in the EBU Catalog database. The EBU Catalog database is an Oracle7 database separate from any of the target databases. Its sole purpose is to host the EBU Catalog.

The suggested minimum size of the EBU Catalog database is 20 MB.

Caution: Oracle strongly recommends that the EBU Catalog database be dedicated exclusively to storing the EBU Catalog, and that it run on a separate machine from all target databases.

 

EBU Catalog

 

The EBU 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 associated 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. The control process is ebu.

 

I/O Processes

 

I/O processes read and write database files between storage disks and the backup media devices.

 

Database Module for Oracle (Media Management API)

 

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.

On Windows NT, EBU ships with a Legato Storage Manager (LSM) as an option. Other media management product provided by members of the Oracle Backup Solutions Program can also be used.

 

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.

 

Figure 1-2 Architecture of the Enterprise Backup Utility

Process   Description  

ebu

 

Monitors all other process and communicates with the target database and the EBU Catalog. The ebu process spawns the Instance Manager if one is not already running

 

master brio

 

Coordinates between ebu and the disk brio and tape brio processes: one master brio process is spawned per parallel I/O stream

 

disk brio

 

Handles read/write of disk files. By default, there are four disk brio processes per I/O stream, if there is no muxing.. If the mux specifier is used, multiple disk brio processes are created for single I/O streams. Disk brio processes are only employed when the "shared memory" I/O model is employed (see Chapter 6)

 

tape brio

 

Handles read/write of tape files. There is one tape brio process per parallel I/O stream. In the Aynchronous I/O model, the tape brio also performs disk I/O simultaneous with tape I/O.

 

brd (Instance Manager)

 

Daemon process that monitors the EBU Catalog and ebu process. The Instance Manager handles cleanup for all backup and restore operations which terminate abnormally.

 

Figure 1-2, "Architecture of the Enterprise Backup Utility" illustrates only a single database being backed up or restored onto one media device. On Unix systems, the Enterprise Backup Utility executables must be installed on a one-per-oracle software owner basis. Figure 1-3, "Single EBU Instance with Two Parallel Data Streams" illustrates a single ebu control process with two spawned I/O processes, streaming to two media devices, using the asynchronous I/O (AIO) model.

Figure 1-3 Single EBU Instance with Two Parallel Data Streams

Understanding EBU Job Steps

Steps steps common to all EBU jobs:

Register jobs:

Backup jobs (excluding BACKUP CATALOG):

If all jobs (as many as three depending on whether archived logs and the backup catalog are also backed up) are succesful, the overall job status will be succesful. If one or more Warnings were issued, the job will be succesful with Warnings. Depending on the kind of error and in what job phase, the job might continue with Warnings or stop altogether.

Backup Catalog job

Common phases up to and including Instance Manager verification are peformed, then it proceeds as described in the above sub-step for the case of catalog backup.

Restore jobs (Excluding RESTORE CATALOG)

Restore Catalog:

New Features in Release 2.2

The following features are new or significantly modified in release 2.2 of the Enterprise Backup Utility.

Available with Oracle 7.3.4

GUI Interface through OEM - Backup Manager, EBU Sub-System

Consult the documentation for Enterprise Manager for additional information on the Backup Manager component.

Oracle Parallel Server Aware

National Language Enabled

NT Availability

Restore Ease of Use

Archivelog Improvements

Logging to Console and EBU log file

EBU, RMAN, and Oracle8

EBU supports backing up 7.1.6 onward up to the last Oracle7 release. RMAN takes

its place with Oracle8 and beyond databases. RMAN cannot back up Oracle7 databases and

EBU cannot back up Oracle8 databases. Backups taken with one cannnot be restored

with the other (EBU and RMAN are not compatible).




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