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rman and really big files [message #73118]

Wed, 04 February 2004 10:08

denise
Messages: 64
Registered: November 2000

Member

How does RMAN handle really big files?� Also, how does RMAN decide what files go into a backup set? Thanks very much, Denise

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Re: rman and really big files [message #73120 is a reply to message #73118]

Wed, 04 February 2004 10:35

Mahesh Rajendran
Messages: 10708
Registered: March 2002
Location: oracleDocoVille

Senior Member
Account Moderator

it can be controlled within RMAN configuration.

quoting docs

Each backup set contains at least one backup piece. If
you do not restrict the backup piece size, then every
backup set contains only one backup piece. To restrict
the size of each backup piece, specify the
MAXPIECESIZE option of the CONFIGURE CHANNEL or
ALLOCATE CHANNEL commands. This option limits backup
piece size to the specified number of bytes

Factors Affecting the Number and Size of Backup Sets
In determining the characteristics of the RMAN backup sets, the basic algorithm is influenced by the following factors:

The number of backupSpec clauses that you specify
The number of input files specified or implied in each backupSpec clause
The number of channels that you allocate
The FILESPERSET parameter, which limits the number of files for a backup set
The MAXSETSIZE parameter (specified on the CONFIGURE and BACKUP commands), which specifies a maximum backup set size
The most important rules in the algorithm for backup set creation are:

Each allocated channel that performs work in the backup job--that is, each channel that is not idle--generates at least one backup set. By default, this backup set contains one backup piece.

--------------------------------------------------------------------------------
Note:
RMAN writes backup pieces sequentially; striping a backup piece across multiple output devices is not supported. For example, RMAN does not simultaneously write half of a backup piece to one disk and the other half to another disk.

--------------------------------------------------------------------------------

RMAN always tries to divide the backup load so that all allocated channels have roughly the same amount of work to do.
The maximum number of datafiles in each backup set is determined by the FILESPERSET parameter of the BACKUP command.
The number of datafiles multiplexed in a backup set is limited by the lesser of FILESPERSET and MAXOPENFILES.
The maximum size of a backup set is determined by the MAXSETSIZE parameter of the CONFIGURE or BACKUP command

Please refer documentation.

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Re: rman and really big files [message #73122 is a reply to message #73120]

Thu, 05 February 2004 10:46

denise
Messages: 64
Registered: November 2000

Member

Thanks for your response. Do you know of any issues with RMAN and really big files? Thanks.

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