Beginning Oracle Database 11g Administration From Novice to Professional

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CHAPTER 16 INSTANCE TUNING
1. The users told the DBA that the problem was restricted to certain parts of the
application only and that there had not been a problem the previous day. On
questioning the application developers, the DBA learned that there had been an
application upgrade the previous night.
2. The DBA used the script to generate Statspack reports for a 1-hour
period for the previous day and the current day. The DBA also traced a number of
database sessions by using the procedure.
3. Examination of the Statspack report for the current day showed large numbers of
events; sessions were waiting, trying to lock an entire table.
These events were not observed in the Statspack report for the previous day. The
table in question was identified by searching through the trace files.
4. The event indicates an unindexed foreign key. If a foreign
key is not indexed, Oracle must lock the entire child table when a record is deleted
from the parent table in the foreign-key relationship. The DBA queried the
, , and views to identify the missing
index and brought this to the attention of the developers.
5. All that was left to do was to implement the solution in a safe and controlled manner.
The developers followed the necessary change control procedures before
creating the necessary index.
Tip A good question to ask during the investigation phase is, “What changed?” If you have installed RDA
as suggested in Chapter 6, you can compare old and new RDA collections by using the option and
determine whether the database environment has changed.
Analyzing DB Time
The best way to analyze database performance is to find out where the database is
spending time. This is powerfully summarized by the Statspack and AWR reports. To
demonstrate this, I used the Swingbench tool 3 to perform large numbers of transactions
in my test database on my laptop. I then used the and scripts
to generate the Statspack and AWR reports for a 1-hour period; the scripts can be found
in . Listing 16-2 shows the first page of the Statspack report; the
AWR report contains similar information.
3. The Swingbench tool can be downloaded from .