Tuning Global Cache - Expert Oracle RAC Performance Diagnostics and Tuning - page 403

The average transfer times (latency) for both the consistent read blocks and current blocks on all servers are
normal. Instance 1 does show an exception over the other instances; however, such exceptions are normal in any
environment and can be safely ignored. Why is the prepare latency high? Or can this be reduced? Let's try to explore
some of the configurations and monitor other areas of the database to determine what can be done to improve on the
prepare time latency of the cluster.

Step 3
A good starting point to look at what could be causing the high latency numbers is to look at Oracle wait interface.
Figure 13-6 illustrates two server pools with two primary application areas. We can generate cluster level AWR
summary reports for these pools. As discussed in Chapter 6, AWR has several command line scripts that can be used
to generate a variety of reports from the AWR. Using the awrgrpti.sql script, generate the following two reports:

1. Report 1 will collect summary for the instance configured in SSKYPOOL1 :

SQL> @$ORACLE_HOME/rdbms/admin/awrgrpti.sql
Specify the Report Type
~~~~~~~~~~~~~~~~~~~~~~~
Would you like an HTML report, or a plain text report?
Enter 'html' for an HTML report, or 'text' for plain text
Defaults to 'html'
Enter value for report_type:
Type Specified: html

Instances in this Workload Repository schema
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

DB Id INSTT_NUM DB Name INSTT_NAME Host
------------ ---------- ------------ ---------------- -----------
. . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . .
Enter value for dbid: 2952283821
Using 2952283821 for database Id
Enter value for instance_numbers_or_all: 1,2,3,4,5
Using instances 1,2,3,4,5 (default 'ALL')

Specify the number of days of snapshots to choose from
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Entering the number of days (n) will result in the most recent
(n) days of snapshots being listed. Pressing <return> without
specifying a number lists all completed snapshots.
Enter value for num_days: 2
Specify the Begin and End Snapshot Ids
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Enter value for begin_snap: 9265
Begin Snapshot Id specified: 9265
Enter value forend_snap: 9279

This generates a summary report for the range of snap (snapshot) id specified for instance 1 through 5. Figure 13-7
illustrates the “Top Timed Events” for these instances.