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One of the most exciting new online features
in Oracle9i is the online table redefinition feature.
The new feature allows Oracle database administrators to redefine
tables online:
- Modify the physical attributes or storage
parameters of a table
- Move a heap table or IOT to a different
tablespace
- Add support for parallel queries
- Add or drop partitioning support
- Recreate a heap table or IOT to reduce
fragmentation
- Change a heap table to IOT and vice versa
- Add, drop, or rename columns in a table
- Transform data in a table
When a table is redefined online, it is accessible
by all read and write operations during the redefinition process.
Administrators have control over when to switch from the original
to the newly redefined table. The switch process is very brief
and is independent of the size of the table or the complexity
of the redefinition. The redefinition process effectively creates
a new table and improves its data block layout efficiency.
The new Oracle9i online table redefinition
feature improves data availability, database performance,
response time and disk space utilization.
Additionally, during an application upgrade,
administrators can start the redefinition process, then periodically
synchronize the new image of the table so that the new image
of the table includes the latest changes to the original table.
This reduces the amount of time to complete the final redefinition
step. Administrators can also validate and use the data in
the new image of the table before completing the redefinition
process. This is a very useful feature for administrators,
who must ensure that the upgrade process goes smoothly.
There are five basic steps to redefine a table:
1. Create a new image of the table with all
of the desired attributes.
2. Start the redefinition process.
3. Create any triggers, indexes, grants and constraints on
the new image of the table.
4. Optionally synchronize and validate data in the new image
of the table periodically.
5. Complete the redefinition of the table.
More Info
Oracle9i
Database Daily Features
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