Beginning Oracle Database 11g Administration From Novice to Professional

CHAPTER 13 RECOVERY 291
Note that LogMiner works as advertised only if you have enabled minimal supplemental
logging. According to the Oracle Database 11g documentation, this “ensures that
LogMiner (and any products building on LogMiner technology) has sufficient information
to support chained rows and various storage arrangements such as cluster tables
and index- organized tables.” The command that enables minimal supplemental logging
is .
A complete discussion of LogMiner can be found in Chapter 18 of Oracle Database
11g Utilities.
Data Recovery Advisor
Physical recovery usually requires the use of Recovery Manager. The two most powerful
RMAN repair commands are simply and . The first command
restores all data files from the last backup. The second command uses the redo logs
and recovers all the changes made since the backup. But full database recovery using the
and commands is not required in all cases. The most
appropriate database strategy is one that is tailored to the situation, and RMAN provides
a wide range of repair options that might overwhelm the beginner. However, Oracle Database
11g also provides a powerful tool called Data Recovery Advisor (DRA) that greatly
simplifies the database administrator’s job.
We demonstrate physical recovery by using DRA to repair corrupt blocks, the same
situation described in my first horror story. In those days, Oracle did not offer the capability
to repair individual blocks while the rest of the database was still being used, though
it did offer the capability to repair individual files. Block recovery is the least invasive of
all recovery operations, and DRA makes the process as easy as it is possible to imagine.
I decided to intentionally corrupt one of the data blocks in the table in the
sample schema, and the view gave me the information I needed to determine
exactly which blocks to corrupt. I shut down the database and modified the file
containing those blocks by using a binary editor. Then I started the database, and everything
worked normally until I tried to list the contents of the table. SQL Developer then
displayed the error dialog shown in Figure 13-2.