||Oracle Tips by Burleson
Chapter 4 Oracle Instance Design
signature for the system. By signature, we mean
trend lines or spikes in user activity. For example, we might see
high user activity every Wednesday afternoon at 1:00 PM. Using this
user audit table, we can quickly identify these user signatures, and
adjust Oracle in order to accommodate these changes and end-user
Related DDL, system errors, and user activity
can easily be captured using the system level triggers. However, it
is clear that system level triggers are not as sophisticated as they
might be, and Oracle indicates that efforts are underway to enhance
system level trigger functionality with the introduction of
Oracle10i in 2003.
However, the judicious use of the system log on
and system log off triggers can provide a very easy and reliable
tracking mechanism for Oracle user activity. For the Oracle
administrator who is committed to tracking user activity over
long-term periods, the user audit table can provide a wealth of
interesting user information, including user usage signatures,
aggregated both by the hour of the day and the day of the week.
Designing Oracle Failover
There are four levels of failover technology
within the Oracle software. Each failover option has it's own
costs, advantages and disadvantages.
Figure 4.3 –Oracle failover options
Oracle9i RAC - This is the most power and
complex of the failover solutions and offers continuous availability
using Transparent Application Failover (TAF).
Oracle Streams - This is a high-speed
replication solution that takes SQL directly from the log_buffer RAM
area and replicates transactions to a remote database. During a
server crash, transactions can be quickly redirected to the
Oracle DataGuard - This is a free option with
Oracle Enterprise Edition and provides for a automated standby
database. Upon server failure, a series of database procedures
synchronizes the standby database and opens it to accept
connections. Oracle DataGuard is free with Enterprise Edition.
Oracle Standby Database -
This is not an Oracle product, and it is a procedure used prior to
Oracle Data Guard to create a standby database. Oracle7 introduced
mechanisms that allow a standby database to be constantly in
recovery mode and to be refreshed from Oracle’s archived redo logs.
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