RMAN backup and recovery operation for a target database are managed by RMAN client. RMAN uses the target database control file to gather metadata about the target database and to store information about its own operations.
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 work of backup and recovery is performed by server sessions running on the target database. A channel establishes a connection from the RMAN client to a target or auxiliary database instance by starting a server session on the instance. The channel reads data into memory, processes it, and writes it to the output device.
When you take a database backup using RMAN , you need to connect to the target database using RMAN Client. 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. For backup you need to allocate explicit or implicit channel to the target database.
An RMAN channel represents one stream of data to a device, and corresponds to one database server session. This session dynamically collect information of the files from the target database control file before taking the backup or while restoring.
RMAN Terminology
A target database: An Oracle database to which RMAN is connected with the TARGET keyword. A target database is a database on which RMAN is performing backup and recovery operations. RMAN always maintains metadata about its operations on a database in the control file of the database.
A recovery Catalog : A separate database schema used to record RMAN activity against one or more target databases. A recovery catalog preserves RMAN repository metadata if the control file is lost, making it much easier to restore and recover following the loss of the control file. The database may overwrite older records in the control file, but RMAN maintains records forever in the catalog unless deletedbytheuser.
Backup Sets: RMAN can store backup data in a logical structure called a backup set, which is the smallest unit of an RMAN backup. One backup set contains one or more datafiles a section of datafile or archivelogs.
Backup Piece: A backup set contains one or more binary files in an RMAN -specific format. This file is known as a backup piece. Each backup piece is a single output file. The size of a backup piece can be restricted; if the size is not restricted, the backup set will comprise one backup piece. Backup piece size should be restricted to no larger than the maximum file size that your file system will support.
Image copies: An image copy is a copy of a single file (datafile, archivelog, or controlfile). It is very similar to an O/S copy of the file. It is not a backupset or a backup piece. No compression is performed.
Snapshot Control file: When RMAN needs to resynchronize from a read-consistent version of the control file, it creates a temporary snapshot control file. The default name for the snapshot control file is port-specific.
Database Incarnation: Whenever you perform incomplete recovery or perform recovery using a backup control file, you must reset the online redo logs when you open the database. The new version of the reset database is called a new incarnation. The reset database command directs RMAN to create a new database incarnation record in the recovery catalog. This new incarnation record indicates the current incarnation
A recovery Catalog : A separate database schema used to record RMAN activity against one or more target databases. A recovery catalog preserves RMAN repository metadata if the control file is lost, making it much easier to restore and recover following the loss of the control file. The database may overwrite older records in the control file, but RMAN maintains records forever in the catalog unless deletedbytheuser.
Backup Sets: RMAN can store backup data in a logical structure called a backup set, which is the smallest unit of an RMAN backup. One backup set contains one or more datafiles a section of datafile or archivelogs.
Backup Piece: A backup set contains one or more binary files in an RMAN -specific format. This file is known as a backup piece. Each backup piece is a single output file. The size of a backup piece can be restricted; if the size is not restricted, the backup set will comprise one backup piece. Backup piece size should be restricted to no larger than the maximum file size that your file system will support.
Image copies: An image copy is a copy of a single file (datafile, archivelog, or controlfile). It is very similar to an O/S copy of the file. It is not a backupset or a backup piece. No compression is performed.
Snapshot Control file: When RMAN needs to resynchronize from a read-consistent version of the control file, it creates a temporary snapshot control file. The default name for the snapshot control file is port-specific.
Database Incarnation: Whenever you perform incomplete recovery or perform recovery using a backup control file, you must reset the online redo logs when you open the database. The new version of the reset database is called a new incarnation. The reset database command directs RMAN to create a new database incarnation record in the recovery catalog. This new incarnation record indicates the current incarnation
No comments:
Post a Comment