Database Reference
In-Depth Information
On the first execution of this script, RMAN will detect that no backup copy exists.
Warnings will be generated but no errors. RMAN will proceed to create the initial copy
of the database. No incremental copy will be created.
On subsequent executions, RMAN will detect that an image copy does exist, and it will
then apply the previous level-1 incremental and then execute another level-1 incremental
backup. Note that on the second run, RMAN will detect that no incremental backup exists
to apply to the data file copy, and a warning will be raised because of this. That is normal.
This method limits the recovery window for your database to one day. For example, if
you executed this script on day 1, day 2, and day 3, after day 3's execution you would not
be able to restore your database to any point before day 3's backup.
You could provide for longer recovery windows by including the
UNTIL TIME
clause. In
this example, we allow for a recovery window of five days:
run {
recover copy of database with tag 'lisa' until time 'sysdate - 5';
backup incremental level 1 for recover of copy with tag 'lisa' database;
}
When configuring incrementally updated backups, you will want to configure the
retention policy of the database to a redundancy of 1. This is because the retention policy
is not honored in the case of this kind of backup. It is, instead, managed by the use of the
UNTIL TIME
clause of the
RECOVER COPY OF DATABASE
command.
RMAN Multisection Backups
Multisection backups
were first available in Oracle Database 11
g
. They provide a way to
parallelize the backup of a given database data file. Since data files had to be contained
wholly within a single backup set, this meant that the backup of that data file was serial-
ized. This can be a bit of a problem if your database consists of one or two huge data files
and several smaller data files. Also, if you are using bigfile tablespaces, the lack of inner-file
backup parallelization could be a big issue.
You perform multisection backups by using the
SECTION SIZE
clause in the
BACKUP
command followed by the desired section size. Here is an example:
RMAN> backup section size 40m database;
In this example, RMAN will divide up each data file into 40MB chunks, and each allo-
cated channel can process those individual 40MB chunks. Note that if you allocate only one
channel, only one chunk at a time will get backed up! Also note that the
SIZE
parameter does
not indicate the size of the resulting backup set piece. Rather, it is the equivalent amount of
data within the data file that each RMAN channel will process. The resulting pieces can vary
wildly in size.
Previous to Oracle Database 12
c
, multisection backups were available only when performing
full backups of the database. Incremental backups and image copies were not supported. Oracle
Database 12
c
now supports multisection backups of full backups, incremental backups, and
image copies.
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