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backup, edit the NetWorker client object for the SQL backup and remove the -Sn option from
the backup command (n is the number of parallel streams per data file; removing this argument
from the backup commands sets it to the default of 1 stream per data file). The default setting
for this is disabled, and most sites do not use Striped Backups with SQL Server.
Different backup job names for the same data: With firmware version 3.4 you should not
have different group names for backing up the same data or they will not deduplicate against
each other. Different job names could be due to having different retention times for the different
backup types (for example, different policy names for full backups vs. incremental backups
or different names for weekly full backups vs. monthly full backups). This limitation is removed
in firmware version 6.0 and higher.
Oracle RMAN Scripting
RMAN scripting provides a highly customizable framework for performing Oracle backups. This
flexibility, however, comes with a large number of possible Oracle backup configurations.
Deduplication has been designed to provide effective deduplication across a significant number
of these configurations. The deduplication algorithms are general enough to handle some generic
scripting cases, while also taking advantage of those instances where the RMAN script provides
specific information concerning the files comprising the backup.
These algorithms are designed to work well in a wide range of RMAN configurations including
data multiplexed by Oracle. There is no deduplication if the RMAN script has either "RMAN
compressed backups" or "RMAN encryption" enabled because these options will always generate
totally unique data for every backup.
Generic RMAN Configuration Optimization
The generic non-optimized RMAN configuration is to use the default values in the RMAN script for
FILESPERSET and MAXOPENFILES and make sure that the control files and spfile backups are not
included in data file backup.
FILESPERSET: This specifies the maximum number of data files to be written into a backup set.
By default, this value is the minimum of 64 and the number of data files divided by the number
of tape drives (defined as channels), rounded up. The number of backup sets is then equal to
the number of data files divided by FILESPERSET, rounded up.
MAXOPENFILES: This determines the maximum number of data files RMAN can have open
at a given time for a single backup set. By default, this value is set to 8. The net result of this
setting will determine how many data files are simultaneously multiplexed by Oracle into each
backup set.
The degree of Oracle multiplexing in a backup set is the smaller of FILESPERSET and
MAXOPENFILES. For example, if you want to backup a database with 175 data files using
8 tape drives (channels) with MAXOPENFILES=3, use the default FILESPERSET value (min(64,
175/8) = 22) in order to minimize the number of backup sets. As a result, RMAN will back
up the database into 8 backup sets (22 data files per backup set) with each of the backup
sets being 3-way Oracle multiplexed.
The MAXSETSIZE command should be equal to or greater than the largest file that is being
backed up to avoid fragmenting the file into multiple backup sets. By default, a single backup
set is created. The MAXSETSIZE setting should be left at the default setting of no entry. The
goal is to minimize the total number of backup sets deduplication must search through to find
the correct match. The backup set number is minimized by reducing the number of channels
and increasing the number of files per backup set. To avoid problems finding matching
backups, the number of channels should not be larger than 30. (This limitation does not apply
to TSM with VLS version 6.0 and higher.)
The generic non-optimized RMAN settings:
FILESPERSET default
Oracle RMAN Scripting
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