Database Reference
In-Depth Information
If the statement is successful, you see the following message:
Control file created.
Finally, alter your database open:
SQL> alter database open;
Summary
This chapter described how to configure and manage control files, online redo log files, enable archiving, and
managing tablespaces and data files. Control files, online redo logs, and data files are critical database files; a normally
operating database can't function without them.
Control files are small binary files that contain information about the structure of the database. Any control files
specified in the parameter file must be available in order for you to mount the database. If a control file becomes
unavailable, then your database will cease operating until you resolve the issue. I highly recommend that you
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.
Tablespaces and data files are where your data is stored. These typically make up the bulk of any backup and
recovery operation. Therefore it's critical that you understand how to work with and manage data files.
The chapters up to this point in the topic have covered tasks connecting to Oracle, performing routine DBA tasks,
and managing critical files. The next several chapters concentrate backup and recovery operations.
