Backing Up Oracle - Computing at Cornell

Units of recovery (which other tables and files need to be recovered to the
same point in time)
Let us look at each of these factors in more detail.
3.1.1 Types of events
We identify five categories of events that may require data recovery:
User error
Statement failure
Transaction failure
Media failure
Disaster
Let us look at each category in more detail.
3.1.1.1 User error
There is considerable opportunity for a user to make an error that causes
data to be lost. For example, a user might inadvertently delete or update rows
in a table or accidentally drop an entire table; or a programmer might make a
logic error that results in data loss or corruption.
RDBMSs provide facilities that reduce the risk or impact of user errors. For
example, you can use RDBMS security to restrict the data that individual
users can access or update. However, it is not possible to eliminate the risk
entirely, and you need to consider how to handle such situations.
One approach is to say that it is the user's responsibility to recover from such
errors. This approach may not be acceptable to users or their management,
however. Another approach is to restore the entire database to the point in
time at which the last backup was taken. This may not be satisfactory to other
users who will lose the updates that they have made to the database since
the last backup.
A third approach is to restore the table space that contains the damaged
table. This approach is likely to be more acceptable than the other two
because:
It removes the responsibility for data recovery from the users.
It may impact fewer users. The number of users impacted will depend
partly on the number of tables included in the affected table space.
You may, however, need to be able to restore individual tables, in which case
you need to have backed up the tables individually.
22 Backing Up Oracle using Tivoli Storage Management