Recovery Manager Architecture
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Recovery Manager Architecture
This chapter describes the Recovery Manager (RMAN) interface and the basic
components of the RMAN environment.
This chapter contains these topics:
About the RMAN Environment
RMAN Command Line Client
RMAN Repository
Media Management
About the RMAN Environment
Recovery Manager (RMAN) is a client application that performs backup and
recovery operations. The Recovery Manager environment consists of the
various applications and databases that play a role in a backup and
recovery strategy.
Table 1-1 lists possible components of the RMAN environment.
Table 1-1 Components of the RMAN Environment
Component Description Required?
Target
database The control files, datafiles, and optional
archived redo logs that RMAN is in charge of
backing up or restoring. RMAN uses the target
database control file to gather metadata about
the target database and to store information
about its own operations. The work of backup and
recovery is performed by server sessions
running on the target database. Yes
RMAN client The client application that manages backup and
recovery operations for a target database. The
RMAN client can use Oracle Net to connect to a
target database, so it can be located on any
host that is connected to the target host
through Oracle Net. Yes
Recovery
catalog
database A database containing the recovery catalog
schema, which contains the metadata that RMAN
uses to perform its backup and recovery No Component Description Required?
operations.
Recovery
catalog
schema The user within the recovery catalog database
that owns the metadata tables maintained by
RMAN. RMAN periodically propagates metadata
from the target database control file into the
recovery catalog. No
Standby
database A copy of the primary database that is updated
using archived logs created by the primary
database. RMAN can create or back up a standby
database. You can fail over to the standby
database if the primary database goes down. No
Duplicate
database A copy of the primary database that you can use
for testing purposes. No
Media
management
application A vendor-specific application that allows RMAN
to back up to a storage system such as tape. No
Media
management
catalog A vendor-specific repository of information
about a media management application. No
Enterprise
Manager A browser-based interface to the Oracle
database, including backup and recovery
through RMAN. No
The only required components in an RMAN environment are the target
database and the RMAN client, but most real-world configurations are more
complicated. One might use an RMAN client connecting to multiple media
managers and multiple target, recovery catalog, and auxiliary databases,
all accessed through Enterprise Manager.
RMAN Session Architecture
The RMAN client application directs database server sessions to perform
all backup and recovery tasks. The meaning of "session" in this sense
depends on the operating system. For example, on UNIX, a server session
corresponds to a server process, while on Windows it corresponds to a
thread within the database service.
The RMAN client itself does not perform backup, restore, or recovery
operations. When you connect the RMAN client to a target database, RMAN
allocates server sessions on the target instance and directs them to perform the operations. The RMAN client uses internal, undocumented
PL/SQL packages to communicate with the target database and recovery
catalog.
RMAN Command Line Client
Use the RMAN command line client to enter commands that you can use to
manage all aspects of backup and recovery operations.
Even when you use the backup and recovery features in Enterprise Manager
that are built on top of RMAN, an RMAN client executes behind the
scenes.
Note:
All RMAN commands for Oracle release 8.1 and higher also
work in Oracle Databse Release 10g.
How RMAN Compiles and Executes Commands
RMAN processes most commands in the two phases discussed in this section:
Compilation Phase
During the compilation phase, RMAN determines which objects the command
will access (for example, resolving a tablespace name into its component
datafiles). Then, RMAN constructs a sequence of remote procedure calls
(RPCs) that instruct the server sessions on the target database to perform
the desired operation.
Execution Phase
During the execution phase, RMAN sends the RPC calls to the target database,
monitors their progress, and collects the results. If more than one
channel is allocated, then RMAN can execute certain commands in parallel
so that all of the channels' target database sessions are concurrently
executing an RPC call.
