Locating control files, Using rollback segments, Using the data dictionary – Oracle Audio Technologies ORACLE9I B10508-01 User Manual

Page 102

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Starter Database Contents


Oracle9i Installation Guide Release 2 ( for HP Alpha OpenVMS

Locating Control Files

The starter database contains three control files


These files are located in the






The files




, and


are automatically included in the Custom



Oracle Corporation recommends that you keep at least three control files

(on separate physical drives) for each database and set the CONTROL_FILES
initialization parameter to list each control file


Table 5–4

describes the database

control files.

Using Rollback Segments

Rollback segments record the old values of data that are changed by each
transaction, whether or not the transaction has been committed. Every database
contains one or more rollback segments. Use rollback segments to provide read
consistency, to roll back transactions, and to recover the database. The rollback
segments of the starter database are as follows:

Rollback segment SYSTEM is contained in tablespace SYS and is used by SYS.

Rollback segments _SYSSMU1$ through _SYSSMU10$ are a pool of rollback
segments that any instance can use if it requires a rollback segment. They are
contained in tablespace UNDOTBS<n> and are used by PUBLIC.

Using the Data Dictionary

The data dictionary is a protected collection of tables and views containing
reference information on the database, its structure, and its users


The data that is

stored in the dictionary includes the following:

Table 5–4

Database Control Files

Control Files





A control file is an administrative file


Oracle9i requires a

control file to start and run the database


The control file

records the physical structure of the database


For example, a

control file contains the database name, and the names and
locations of the database data files and redo log files.

See Also:

Oracle9i Database Administrator’s Guide for more

information on setting this initialization parameter value.