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Defining Rollback Segments

Rollback segments (RBS) are used when a process is performing inserts, updates, or deletions (DML).

Oracle assigns each transaction to a rollback segment. As a rule of thumb, the total number of rollback segments required should be based on four concurrent transactions per rollback segment. However, database administrators should monitor their database and configure rollback segments based on the requirements of the Siebel applications running.

To make sure you have sufficient rollback segments for larger implementations

  1. Create multiple rollback segments, each with multiple extents, at least, initially.
  2. Calculate 5-10 active transactions (user activity consisting of an insert, update, or deletion) per extent, and from two to six extents per rollback segment.

To make sure you have sufficient rollback segments for smaller implementations

  1. Create a single, much larger rollback segment for Siebel Server components, such as Enterprise Integration Manager (EIM). Siebel Server components can point directly to this rollback segment when performing long-running queries.
  2. To promote optimal system performance, create your rollback segments in a dedicated tablespace on a dedicated disk. Rollback segments typically support high I/O rates, so this action will improve system performance measurably.

 Siebel Server Installation Guide for Microsoft Windows 
 Published: 25 June 2003