When a transaction fails, the data contained in the rollback segment is re-inserted back into the database, thus restoring its integrity. Once the transaction is "committed" or restored, the rollback segment is flushed clean. Rollback segments are created in a tablespace dedicated for them. Since most ENOVIA Live Collaboration transactions are small, a segment size of 64 k will cover most of them. The recommended extent size is 128k with a minimum of 10 extents. However, there are some conditions, such as during ENOVIA Live Collaboration upgrades or a business definition modification that is widely referenced, that may require a large rollback segment. A rule of thumb is that there should be one rollback segment for every ten concurrent users. Either the "Storage Manager" or "SQL*Plus" may be used for this purpose. Once created, all new rollback segments must be identified in init<SID>.ora, as described below. For large scale concurrent systems (500+ processes) rollback segments might be spread across multiple tablespaces on different spindles. This is known as "striping" the rollback segments. | |||||||