I??™ll also show
how transportable tablespaces are a distinct advantage in a VLDB environment because they
bypass some of the export/import steps required in versions prior to Oracle9i to move the contents
of a tablespace from one database to another. When tablespaces in a VLDB environment approach
the exabyte size, both the extra space required for a traditional export and import operation and
the time it takes to perform the export may become prohibitive. If you are using Oracle 11g, your
tablespaces may even be transportable between different hardware and software platforms with
minimal or no extra effort.
Next, we will review the various types of nontraditional (non-heap-based) tables that are often
leveraged in a VLDB environment. Index-organized tables (IOTs) combine the best features of a
traditional table with the fast access of an index into one segment; we??™ll review some examples
of how IOTs can now be partitioned in Oracle 11g. Global temporary tables dramatically reduce
space usage in the undo tablespace and redo logs for recovery purposes because the table contents
only persist for the duration of a transaction or a session. External tables make it easy to access
data in a non-Oracle format as if the data was in a table; as of Oracle 10g, external tables can be
created using Oracle Data Pump, covered at the end of this chapter. Finally, the amount of space
occupied by a table can be dramatically reduced by using an internal compression algorithm
when the rows are loaded using direct-path SQL*Loader and create table as select statements.
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