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Saturday, June 30, 2007

Oracle 8i Database New Features

Oracle 8i New Features

Drop Column

A new drop column capability allows the DBA to easily remove unused columns in the database. Previously, it was necessary to use the export/import utilities.

Locally Managed Tablespaces

Prior to Oracle8i, management of free and used extents within a tablespace relied heavily on data dictionary tables. Now, Oracle introduces a new mechanism for managing space within a tablespace: locally managed tablespaces. All extent information is tracked in the tablespace itself, using bitmaps.

Online Index Creation, Rebuild, and Defragmentation

Creating or rebuilding an index on a table improves query performance when completed, but can be a very time-consuming operation. For large tables, it can require several hours of downtime because it forces a lock on the table and prevents concurrent DML. This is called offline index build.

Oracle8i supports the online creation or rebuilding of an index that works for partitioned or nonpartitioned B*-tree indexes, including index-organized tables. Since the table is not locked, DML operations and queries can execute on the base table while the index is being built.

Alternatively, if you do not want to rebuild the index because of space or other considerations, then the new COALESCE keyword may be specified to defragment the index. In either case, performance is improved and space recovered.

Nonpartitioned Table Reorganization

A new MOVE clause used in an ALTER TABLE statement provides a means to easily reorganize a nonpartitioned table by allowing the user to move data into a new segment while preserving all views, privileges, etc. defined on the table. The operation is performed offline.

Online Read-Only Tablespaces

Oracle8i improves the performance of the operation that places a tablespace in read-only mode. A tablespace in Oracle8i can be placed in read-only mode when there are no outstanding transactions in that tablespace alone, unlike previous versions of Oracle where the operation completed only when there were no outstanding transactions in the entire database.

Temporary Tables

A temporary table is a table with session-specific or transaction-specific data. It is empty when the session or transaction begins, and discarded at the end of the session or transaction. Its definition is visible to all sessions but the data is visible to, and can be queried by, only the session that inserts the data into the table

Note: Above is not complete list of new features for more details please refer documentation.

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