RMAN: Maximum backup set size, piece size, rate, open files

Andrey Volkov

Andrey Volkov

System, network administration + DBA. And a little programmer!)) See Author profile.

RMAN provides a flexible number of channel configuration commands. You will occasionally need to use them, depending on special circumstances and the requirements for your database. Here are some of the options:

  • Maximum backup set size
  • Maximum backup piece size
  • Maximum rate
  • Maximum open files

By default the maximum backup set size is unlimited. You can use the MAXSETSIZE parameter with the CONFIGURE or BACKUP command to specify the overall maximum backup set size. Make sure the value of this parameter is at least as great as the largest data file being backed up by RMAN. Here is an example:

RMAN> configure maxsetsize to 2g;

Sometimes, you may want to limit the overall size of a backup piece because of physical limitations of storage devices. Use the MAXPIECESIZE parameter of the CONFIGURE CHANNEL or ALLOCATE CHANNEL command do this; for example,

RMAN> configure channel device type disk maxpiecesize = 2g;

If you need to set the maximum number of bytes that RMAN reads each second on a channel, you can do so, using the RATE parameter. This configures the maximum read rate for channel 1 to 200MB per second:

configure channel 1 device type disk rate 200M;

If you have a limit on the number of files you can have open simultaneously, you can specify a maximum open files number via the MAXOPENFILES parameter:

RMAN> configure channel 1 device type disk maxopenfiles 32;

You may need to configure any of these settings when you need to make RMAN aware of some OS or hardware limitation. You’ll rarely need to use these parameters but should know of them.

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