Database Reference
In-Depth Information
Previous versions of this text (and OCP exams) contained significant cov-
erage of Oracle Enterprise Manager (OEM). The Oracle Database 12
c
OCP
exam contains no coverage specific to OEM and much more coverage on
user-based backup and recovery. As a result, there is little coverage of
OEM within this text.
Database Server
The
database server
is the principal mechanism used to back up the
database. Built into the core of the Oracle kernel code are stored packages used by RMAN
to back up, restore, and recover the database. RMAN cannot execute backup, restore, or
recover operations without having first attached to the database server. Depending on the
operation, the database will need to be opened in nomount, mount, or open mode.
Control File
The
database control file.
is used to store RMAN-related information for
each database. The control file is the principal storage mechanism for all RMAN-related
records. All records with respect to database backups, archive-log backups, and control-file
backups are stored in the control file.
Control files have limitations with respect to how many RMAN records they
can hold, and as a result, certain retention requirements may call for the use
of a recovery catalog to augment a control file. RMAN provides an automated
means of backing up the control file and restoring it when a control file is not
readily available. This method is called a
control-file autobackup
.
Recovery Catalog
The
recovery catalog
is an optional component that stores RMAN-related
information inside an Oracle Database. This is similar to the RMAN repository stored in the
control file, but the recovery catalog provides some additional features and longer-term stor-
age of RMAN records. The recovery catalog is a special schema that contains backup-related
information in a set of tables. During normal database operations, RMAN will synchronize
the database control file with the recovery catalog, ensuring that the recovery-catalog schema
is in synchronization with the database control file.
Database Pfile or Spfile
You should already be familiar with the
database parameter file
(pfile)
and the
server parameter file (spfile).
. These files are critical to RMAN operations
because they contain parameters that impact RMAN operations. RMAN can be used to
back up and recover an spfile using an option called
autobackup
. Pfiles cannot be backed
up with RMAN.
Backup Media and the Media Management Library
Obviously, if RMAN is going to back
up your database, it needs to back it up somewhere. RMAN, out of the box, allows you to
back up your database to disk. This can be the local disk, or a network-attached disk (in other
words, NFS) can be used. RMAN also offers the Media Management Library. The MML is
an API set that media vendors (for example, tape-drive vendors) can write to and that allows
RMAN to communicate directly with their products.
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