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Oracle Tips by Burleson |
OCP Instructors Guide for
Oracle DBA Certification
Chapter 5 - Oracle Database
Objects
Oracle9i Tablespace Changes
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Because a datafile specification was not provided, the tablespace is
Oracle managed. The datafile clause is only optional if the
DB_CREATE_FILE_DEST initialization parameter is set. The parameter
specifies an operating system directory that is the default storage
location for Oracle managed datafiles. The operating system
directory must already exist and must have the proper security
permissions to allow Oracle to create files in it. If a datafile
specification and SIZE parameter are not specified, a 100-megabyte
file is created by default. During tablespace creation, the database
server selects a file name for the Oracle managed file and creates
the file in the directory specified in the db_create_file_dest initialization parameter. When the tablespace is dropped, Oracle automatically removes the Oracle
managed files associated with the dropped tablespace. By default, an
Oracle managed datafile is autoextensible with an unlimited maximum
size.
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The tablespace will be locally managed because
we did not specify EXTENT MANAGEMENT DICTIONARY during creation.
Oracle has changed the default from dictionary managed in Oracle8i
to locally managed in Oracle9i. Locally managed tablespaces track
all extent information in the tablespace itself, using bitmaps.
Tracking extents in bitmaps improves speed and concurrency of space
operations.
Administrators are able to override Oracle
managed extents by specifying EXTENT MANAGEMENT DICTIONARY in the
tablespace definition. Dictionary managed tablespaces rely on data
dictionary tables to track space utilization within the tablespace.
The SYSTEM tablespace is always dictionary managed.
The above text is
an excerpt from:
OCP Instructors Guide for Oracle DBA Certification
A Study Guide to Advanced Oracle Certified Professional Database
Administration Techniques
ISBN 0-9744355-3-8
by Christopher T. Foot
http://www.rampant-books.com/book_2003_2_OCP_print.htm
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