Databases Reference
In-Depth Information
configure your database with at least three control files. If one control file becomes unavailable, you can replace it
with a copy of a good existing control file. It's critical that you know how to configure, add, and remove these files.
Online redo logs are crucial files that record the database's transaction history. If you have multiple instances
connected to one database, then each instance generates its own redo thread. Each database must be created with
two or more online redo log groups. You can operate a database with each group's having just one online redo log
member. However, I highly recommend that you create your online redo log groups with two members in each group.
If an online redo log has at least one member that can be written to, your database will continue to function. If all
members of an online redo log group are unavailable, then your database will cease to operate. As a DBA you must be
extremely proficient in creating, adding, moving, and dropping these critical database files.
Archiving is the mechanism for ensuring you have all the transactions required to recover the database. Once
enabled, the archiver needs to successfully copy the online redo log after a log switch occurs. If the archiver can't write
to the primary archive destination, then your database will hang. Therefore, you need to map out carefully the amount
of disk space required and how often to back up and subsequently remove these files.
The chapters up to this point in the topic have covered tasks such as installing the Oracle software; creating
databases; and managing tablespaces, data files, control files, online redo log files, and archiving. The next several
chapters concentrate on how to configure a database for application use and include topics such as creating users and
database objects.
