Oracle DB Tuning recipe

假设操作系统和数据库的数据都已经收集了，以下是Oracle DB Tuning的一些步骤（可据经验增加）
1. Is the response time/batch run time acceptable for a single user on an empty or
lightly loaded system?
If it is not acceptable, then the application is probably not coded or designed
optimally, and it will never be acceptable in a multiple user situation when system
resources are shared. In this case, get application internal statistics, and get SQL
Trace and SQL plan information. Work with developers to investigate problems in
data, index, transaction SQL design, and potential deferral of work to
batch/background processing.

2. Is all the CPU being utilized?
If the kernel utilization is over 40%, then investigate the operating system for
network transfers, paging, swapping, or process thrashing. Otherwise, move onto
CPU utilization in user space. Check to see if there are any non-database jobs
consuming CPU on the system limiting the amount of shared CPU resources, such
as backups, file transforms, print queues, and so on. After determining that the
database is using most of the CPU, investigate the top SQL by CPU utilization.
These statements form the basis of all future analysis. Check the SQL and the
transactions submitting the SQL for optimal execution. Oracle provides CPU
statistics in V$SQL and V$SQLSTATS.
If the application is optimal and there are no inefficiencies in the SQL execution,
consider rescheduling some work to off-peak hours or using a bigger system.

3. At this point, the system performance is unsatisfactory, yet the CPU resources are
not fully utilized.
In this case, you have serialization and unscalable behavior within the server. Get
the WAIT_EVENTS statistics from the server, and determine the biggest
serialization point. If there are no serialization points, then the problem is most
likely outside the database, and this should be the focus of investigation.
Elimination of WAIT_EVENTS involves modifying application SQL and tuning
database parameters. This process is very iterative and requires the ability to drill
down on the WAIT_EVENTS systematically to eliminate serialization points.
See Also: Oracle Database Reference for more information on
V$SQL and V$SQLSTATS