• To coalesce data. When there are deletes on a table, the rows become spread out in a data block in the table. This honey-combing will hurt performance during inserts as Oracle will try to find any existing space that can be used prior to allocating new space.
• When data is removed from a table in Oracle, the database retains the space that had stored the deleted data. As a result, after removing data, the system may not see a significant change in performance, because some SQL statements scan the empty blocks. Further, no disk space is reclaimed since it is still retained by the tablespace. This is particularly true when using the data purging and archiving features in RSA Identity Governance & Lifecycle which remove large amounts of data.
• Oracle uses b-tree indexes and similar to a table, when data is deleted, the leaf blocks of the index will be maintained even though they may be empty. They will only be reused if there is data that matches that leaf.. So a primary key will never have another value that matches the leaves since it is unique. Therefore you have data blocks that will never be reused. An additional problem with this is that a full index scan will have to go through and read the empty blocks.
• Improve performance in the user interface.
• Reduce the size of a database backup and the time it takes to perform a backup or a restore of the database.
• Reduce the time it takes to perform database statistics.

Database size and performance can be controlled by:

• Removing unnecessary data
• Reclaiming unused database space
• Reducing fragmentation

How these tasks are accomplished in RSA Identity Governance & Lifecycle depends on your RSA Identity Governance & Lifecycle version. 
 

7.1.0, 7.1.1

• Data Archiving (Admin > System > Data Management tab > Archiving)

You create a data archive to remove older data from active use within the RSA Identity Governance and Lifecycle system, while retaining a backup of the data to adhere to internal data retention policies or for auditing purposes. Archiving data reduces the size of the database and the resources needed by the database. When you create a data archive, data that meets the archive criteria is backed up to an Oracle Data Pump backup file and then purged from the system. As part of the archive process, archived data is completely removed from the system and cannot be accessed or seen anywhere within the RSA Identity Governance and Lifecycle user interface.

Benefits: Use of this feature frees up space but no space is actually reclaimed until segment advisor is run. (See below.)

• Data Purging (Admin > System > Data Management tab > Purging)

• Segment Advisor

• Database export followed by a database import.

7.0.1, 7.0.2

• Upgrade

• Data Purging (Admin > System > Data Management tab > Purging)

• Segment Advisor

• Database export followed by a database import.

7.0.0 and below

• Upgrade

• Data Purging

• Segment Advisor

• Database export followed by a database import.