Global temporary tables
create a common table definition available to all database users; in a VLDB, a global temporary
table shared by thousands of users is preferable to each user creating their own definition of the
table, potentially putting further space pressure on the data dictionary. External tables allow you
to use text-based files outside of the database without actually storing the data in an Oracle table.
Partitioned tables, as the name implies, store tables and indexes in separate partitions to keep the
availability of the tables high while keeping maintenance time low. Finally, materialized views
preaggregate query results from a view and store the query results in a local table; queries that
use the materialized view may run significantly faster because the results from executing the view
Chapter 16: Managing Large Databases 553
do not need to be re-created. We will cover all these table types to varying levels of detail in the
following sections.
Index-Organized Tables
You can store index and table data together in a table known as an index-organized table (IOT).
Significant reductions in disk space are achieved with IOTs because the indexed columns are not
stored twice (once in the table and once in the index); instead, they are stored once in the IOT
along with any non-indexed columns. IOTs are suitable for tables where the primary access
method is through the primary key, although creating indexes on other columns of the IOT is
allowed to improve access by those columns.
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