Oracle Database 11 g - Online Public Access Catalog

CHAPTER 12 ■ DATA WAREHOUSING 539tablespaces, DBAs can place older data on less expensive storage tiers. New data continues tobe stored in tier 1 storage, while the older data can be migrated to less expensive tier 2, 3, and 4storage. In addition, the older data can be compressed, thus further reducing storage costs.Partitioning also provides to DBAs the flexibility to make tablespaces read-only. By implementingthe skip readonly tablespace syntax to the RMAN backup architecture, significantlyless space will be required for backups performed to disk and tape.Many companies do not implement partitioning because of the additional licensing costassociated with it. If DBAs, backup administrators, developers, and senior management carefullyanalyze their application to look for ways to implement partitioning with read-only tablespaces,the Oracle partitioning option pays for itself. For large companies that have storage in theterabyte or even petabyte range, the Oracle partitioning option can save them money instorage and backups.Oracle offers four main partitioning mechanisms:• Composite partitioning• Hash partitioning• List partitioning• Range partitioningBased on the business requirement, each of the partitioning methods has its appropriatejustified need in today’s corporations. Oracle Database 11g improves partitioning options andprovides new options to meet today’s demanding requirements.New to Oracle Database 11g are numerous techniques for partitioning table data to increasethe performance and organization of your corporate data. These partitioning techniquesinclude the following:• Reference that allows tables with a parent-child relationship to be logically equipartitionedby inheriting the partition key from the parent table without duplicating the key columns• Interval that automatically creates maintenance partitions for range partitions• Extended composite that allows data to be partitioned along two dimensions• Virtual columns that allow virtual columns to be defined as partition key columnsPartition AdvisorPartitioning advice is available within the SQL Access Advisor as part of Enterprise Manager orthe command-line interface. In Oracle Database 11g, the SQL Access Advisor will also recommendpartitions. In addition to the normal recommendations to create or drop indexes, materializedviews, and materialized view logs, Oracle will recommend to partition existing tables andindexes to improve performance. The Partition Advisor provides the appropriate SQL syntax tocreate a temporary partitioned table, copy data, and rename the table to the original table name.Furthermore, the Partition Advisor will show the potential performance improvements fromimplementing the recommended partitions. The Partition Advisor is integrated with the SQLAccess Advisor and is licensed under Oracle’s Tuning Pack.In the initial SQL Access Advisor screen, available as an option on the Advisor Centralscreen, you can click the option to recommend new access structures, as shown in Figure 12-1.