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Oracle® Database Backup and Recovery Advanced User's Guide 10g Release 2 (10.2) Part Number B14191-02 |
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# Configuring the Maximum Size of Backup Sets and Pieces

The `CONFIGURE` `MAXSETSIZE` command limits the size of backup sets created on a channel. This `CONFIGURE` setting applies to any channel, whether manually allocated or configured, when the `BACKUP` command is used to create backup sets.

You can set `MAXSETSIZE` in bytes (default), kilobytes (`K`), megabytes (`M`), and gigabytes (`G`). The default value is given in bytes and is rounded down to the lowest kilobyte value. For example, if you set the maximum set size to 2000, then RMAN rounds down this value to 1 kilobyte (1024 bytes). If you set the maximum set size to 2049, then RMAN rounds down this value to 2 kilobytes (2048 bytes).

The value set by the `CONFIGURE MAXSETSIZE` command is a default for the given channel. You can override the configured `MAXSETSIZE` value by specifying a `MAXSETSIZE` option for an individual `BACKUP` command.

Assume that you issue the following commands at the RMAN prompt:

    CONFIGURE DEFAULT DEVICE TYPE TO sbt;
    CONFIGURE CHANNEL DEVICE TYPE sbt PARMS 'ENV=(NSR_DATA_VOLUME_POOL=first_pool)';
    CONFIGURE MAXSETSIZE TO 7500K;
    BACKUP TABLESPACE users;
    BACKUP TABLESPACE tools MAXSETSIZE 5G;

The results will be as follows:

- The backup of the `users` tablespace uses the configured `sbt` channel and the configured default `MAXSETSIZE` setting of `7500K`.

- The backup of the `tools` tablespace uses the `MAXSETSIZE` setting of `5G` used in the `BACKUP` command.

  Note: There is no equivalent to `MAXSETSIZE` for controlling the size of image copies. Since an image copy is an exact duplicate of the file being backed up, its size must be identical to the source file. This fact can present a problem with some older operating systems which limit the size of individual files. If you are using a raw partition to store a 10GB datafile, and your operating system only supports 4GB files on the file system, you cannot take image copy backups of that file.

  See Also: Oracle Database Backup and Recovery Reference for `BACKUP` syntax

## Showing the Default Maximum Size of Backup Sets: SHOW MAXSETSIZE

You can use `SHOW MAXSETSIZE` to view the maximum backup set size set using `CONFIGURE` `MAXSETSIZE`. The size of a backup set is measured in the total bytes of the included backup pieces. After connecting to the target database and recovery catalog (if you use one), issue the `SHOW` `MAXSETSIZE` command. For example, enter:

    SHOW MAXSETSIZE;      # shows the CONFIGURE MAXSETSIZE settings

Sample output for `SHOW` `MAXSETSIZE` follows:

    RMAN configuration parameters are:
    CONFIGURE MAXSETSIZE TO 3072K;