Justifying Oracle Partitioning Oracle Tips by Burleson Consulting July 22, 2003

 

Partitioning is a divide-and-conquer approach to improving Oracle maintenance and SQL performance.  Anyone with un-partitioned databases over 500 gigabytes is courting disaster.  Databases become unmanageable, and serious problems occur: 

-         Files recovery takes days, not minutes

-         Rebuilding indexes (important to re-claim space and
          improve performance) can take days

-         Queries with full-table scans take hours to complete

-         Index range scans become inefficient

There are many compelling reasons to implement partitioning for larger databases, and partitioning has become the de-facto standard for systems over 500 gigabytes.  Oracle partitioning has many benefits to improve performance and manageability:

• Stable - Partitioning is a very stable technology and has been used in Oracle since Oracle8, back in 1997.  Each new release of Oracle improves partitioning features.
   

• Robust – Oracle9i partitioning allows for multi-level keys, a combination of the Range and List partitioning technique. The table is first range-partitioned, and then each individual range-partition is further sub-partitioned using a list partitioning technique. Unlike composite Range-Hash partitioning, the content of each sub-partition represents a logical subset of the data, described by its appropriate Range and List partition setup. 
   

• Faster backups - A DBA can back-up a single partition of a table, rather than backing up the entire table, thereby reducing backup time.
   

• Less overhead – Because older partitioned tablespaces can be marked as read-only, Oracle has less stress on the redo logs, locks and latches, thereby improving overall performance.  For more details, read Robert Freeman's discussion of read-only tablespace performance.
   

• Easier management – Maintenance of partitioned tables is improved because maintenance can be focused on particular portions of tables. For maintenance operations across an entire database object, it is possible to perform these operations on a per-partition basis, thus dividing the maintenance process into more manageable chunks.
   

• Faster SQL – Oracle is partition-aware, and some SQL may improve is speed by several orders of magnitude (over 100x faster).

- Index range scans – Partitioning physically sequences rows in index-order causing a dramatic improvement (over 10x faster) in the speed of partition-key scans.

-  Full-table scans – Partition pruning only access those data blocks required by the query.

-  Table joins – Partition-wise joins take the specific sub-set of the query partitions, causing huge speed improvements on nested loop and hash joins.

-  Updates – Oracle parallel query for partitions improves batch load speed by

In sum, partitioning has a very-fast payback time and the immediate improvements to performance and stress reduction on the Oracle server makes it a slam-dunk decision.

 

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