An image
copy is a clone of a single data file, archived redo log, or control file. An
image copy can be created with the BACKUP AS COPY command or with an operating
system command. When you create the image copy with the RMAN BACKUP AS COPY
command, the server session validates the blocks in the file and records the
copy information in the control file.
An image
copy has the following characteristics:
•
An
image copy can be written only to disk. When large files are being considered,
copying may take a long time, but restoration time is reduced considerably
because the copy is available on the disk.
•
If
files are stored on disk, they can be used immediately by using the SWITCH
command in RMAN, which is equivalent to the ALTER DATABASE RENAME FILE SQL
statement.
In an image
copy, all blocks are copied, whether they contain data or not, because an
Oracle database process copies the file and performs additional actions such as
checking for corrupt blocks and registering the copy in the control file. To
speed up the process of copying, you can use the NOCHECKSUM parameter. By
default, RMAN computes a checksum for each block backed up, and stores it with
the backup. When the backup is restored, the checksum is verified.
RMAN>
BACKUP AS COPY DATAFILE '/ORADATA/users_01_db01.dbf';
RMAN> BACKUP AS COPY ARCHIVELOG LIKE '/arch%';
RMAN> BACKUP AS COPY ARCHIVELOG LIKE '/arch%';
