Wednesday, January 20, 2010

Chapter 10. Partitioning











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Chapter 10. Partitioning







Over the past 15 years,



hard disk capacities have evolved

from around 10 MB to over 100 GB, and capacities are still growing.

Disk arrays are fast approaching the 100 terabyte range. No matter

how much storage is available, however, there is always a way to

exhaust it. As databases grow in size, day-to-day operations become

more and more challenging. For example, finding the time and

resources to rebuild an index containing 100 million entries can

prove quite demanding. Prior to Oracle8, database administrators

would meet this challenge by manually breaking a large table into

several smaller tables. Although the pieces could be hidden behind a

special type of view (called a partition view)

during a query, all DML statements had to be performed against the

individual tables, thereby exposing the partitioning scheme to the

database developers and users.





Starting with Version 8.0, Oracle provided a means for breaking a

table into multiple pieces while preserving the look and feel of a

single table. Each piece is called a partition,

and, although every partition must share the same columns,

constraints, indexes, and triggers, each partition can have its own

unique storage parameters. While administrators generally deal with

individual partitions when allocating storage and performing backups,

developers may choose to deal with either the entire table or with

individual partitions.



















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