Database Reference
In-Depth Information
CHAPTER 17
■ ■ ■
DBMS_BACKUP_RESTORE
T
he package
DBMS_BACKUP_RESTORE
is undocumented in the
Oracle9i Supplied PL/SQL Pack-
ages and Types Reference
as well as in
Oracle Database PL/SQL Packages and Types Reference
of
Oracle10
g
and subsequent releases. Restoring database files with Recovery Manager (RMAN)
requires either that a control file with bookkeeping information on the files to restore is mounted
or that a database session to an RMAN catalog with like information is available.
DBMS_BACKUP_
RESTORE
makes possible a restore without RMAN in a disaster scenario. Such a scenario is char-
acterized by the loss of all current control files, and the lack of or unavailability of a recovery
catalog or control file backup that contains records of the most recent data file and archived
redo log backups. Note that bookkeeping information on backups is aged out of the control file
depending on the setting of the initialization parameter
CONTROL_FILE_RECORD_KEEP_TIME
. The
default setting of this parameter is merely seven days.
Recovery Manager
Recovery Manager (RMAN) is a backup and recovery utility that was introduced with Oracle8.
RMAN is a database client just like SQL*Plus, Data Pump Export/Import, SQL*Loader, or any
other program that can interact with an ORACLE instance through Oracle Call Interface (OCI).
RMAN itself does not back up or restore any part of an ORACLE database. If you recall that
RMAN can run on any machine within a network, connect to an ORACLE instance on a remote
database server, and perform backup and recovery, it is quite clear that RMAN neither needs to
nor has the capability to read or write any database files. Instead, RMAN uses the undocumented
package
DBMS_BACKUP_RESTORE
to instruct an ORACLE instance to perform backup and restore
operations.
The ORACLE DBMS supports mounted file systems and so-called media managers for
storage of backups. A media manager is software that integrates with an ORACLE instance
through the SBT (System Backup to Tape, see
Oracle Database Backup and Recovery Basics 10g
Release 2
) interface and is capable of controlling tape devices for storing backups. The SBT
interface is a specification by Oracle Corporation. The specification is disseminated to soft-
ware companies wishing to support RMAN-based backup and recovery. The SBT interface is
not documented in ORACLE DBMS documentation and is usually implemented as a shared
library (a.k.a. dynamic link library or DLL), which is used by the program
$ORACLE_HOME/bin/
oracle
(or
oracle.exe
on Windows) that implements an ORACLE instance. Oracle Corporation
provides an implementation of the SBT interface that is linked with the executable
oracle[.exe]
by
default. Usually, this executable is relinked with a shared library shipped with media manage-
ment software, to enable an ORACLE instance to talk to a media manager.
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