Oracle Session Tracing Part IV
January 6, 2005
Part IV in our series will focus on determining which internal
Oracle views hold the information to our enabled statistical gathering.
In Part I, we
learned how to set the CLIENT_IDENTIFIER session variable to more accurately
pinpoint resource consumption for an individual user or group of users.
II, we learned how to set the ACTION and MODULE name so that we could track
where in our code transactions were being executed and track the use of resources
by transaction type or section of code.
III, we focused on enabling tracing of statistics through the DBMS_MONITOR
Now in part IV of this series we will look at the internal views
within Oracle that keep track of the enabled statistics gathering enabled in
In Part III, we left off displaying the enabled traces and
statistic gatherings we enabled through the DBMS_MONITOR package. Recall that
in Part III we queried the DBA_ENABLED_AGGREGATIONS view and had a listing such
as in Listing 1. Table 1 gives a breakdown of the
DBA_ENABLED_AGGREGATIONS view as I have renamed some of the columns for Listing
SQL> SELECT * FROM DBA_ENABLED_AGGREGATIONS ;
AGGREGATION SERVICE MODULE ACTION
-------------------- -------------------- -------------------- --------------------
SERVICE_MODULE ACCT PAYROLL
is the type of statistical aggregation being done. This relates to the actual
procedure called in the DBMS_MONITOR package. In Listing 1, we have called
the CLIENT_ID_STAT_ENABLE and SERV_MOD_ACT_STAT_ENABLE procedures
This is the CLIENT_IDENTIFIER or SERVICE_NAME in the call
The module name
The action name
In the last three parts of this series, we have also zeroed
in on setting different session environment variables. Those variables were
CLIENT_IDENTIFIER, ACTION, and MODULE. We have also tracked some of the
sessions by SID, SESSION_ID, SERVICE_NAME, and SERIAL#. I thought it might be
interesting to look at where within Oracle's internal views these columns might
be defined since this could help us in future needs of our investigation.
Instead of searching through the endless documentation of Oracle, I instead
decided to produce a query (Listing 2) in which I queried the
DBA_TAB_COLUMNS view to look at what internal Oracle views or objects have
these columns in common. From the output, I can then look at the definitions of
those named objects that intrigue me. Listing 2 is only a partial
listing and I encourage you to execute the query and see the total output. That
way if you are ever interested in searching for a single column or combination
of columns you will know where within the Oracle internal views this
information is stored. Do not take this output too lightly. If you remember
that we were enabling statistics gathering and tracing in the previous parts to
this article for combinations of these columns, you can quickly see where in
this listing the information is kept and where aggregates on columns are
stored. Also, be warned that most of the output you will see are for Oracle's
workload repository, advisories, and snapshots mechanisms and are not of any
real use unless you are using those utilities. For us I have only left the
objects we will be concerned with for looking at the gathered statistics we
have enabled. Table 2 gives a brief explanation of these views, how you might
use them, and some things to look out for.
Query to investigate Oracle Views that contain our
from (select owner,table_name,column_name
where owner = 'SYS'
and column_name in ('SID', 'SESSION_ID',
'SERVICE_NAME', 'ACTION', 'MODULE', 'SERIAL#'))
group by table_name
order by table_name
TABLE_NAME SID ID NAME ACTION MODULE SERIAL#
------------------------------ --- ------ ------- ------ ------ -------
DBA_HIST_ACTIVE_SESS_HISTORY 1 1 0 1 1 0
V_$ACTIVE_SESSION_HISTORY 1 1 0 1 1 0
V_$CLIENT_STATS 0 1 0 0 0 0
V_$SERVICE_STATS 0 0 1 0 0 0
V_$SERV_MOD_ACT_STATS 0 0 1 1 1 0
view is a holding area for sampled session data performed on your behalf from
the Oracle engine. This data is sampled once per second and is a great resource
for determining where the true bottleneck lies in your system.
Use this view in
conjunction with setting the CLIENT_IDENTIFIER, ACTION, and MODULE to
aggregate (GROUP BY) and find the largest consumers of resources within your
Take a look at
another article I wrote entitled "True Session Wait Activity in Oracle
10g" for how to use this view.
This view is
just an historical representation of the V$ACTIVE_SESSION_HISTORY view above.
While it is good for some historical information, be warned that it does not
contain all of the collected statistics that were captured in the
V$ACTIVE_SESSION_HISTORY view. Please read the above-mentioned article to get
an understanding of how this works.
- If you
have enabled any statistics for a CLIENT_IDENTIFIER you will see the
aggregated statistics for that CLIENT_IDENTIFIER that are currently active in
statistics are only good for current activity and troubleshooting and thus
should only be used for getting a glimpse of what clients are consuming the
for a quick current view but if you need to drill to a particular client you
will end up going to V$ACTIVE_SESSION_HISTORY.
a reduced set of statistics that can be used to determine how well an
instance is performing for the requests made upon it.
typically the SID_NAME but be aware it may be different if you are not
connecting through TNS.
The use of these views is quite straightforward. You need
only query them for the statistical aggregation you have set up through the
DBMS_MONITOR package. The real difficulty lies in setting up those aggregations
stepped through in earlier parts of this series. Next time we will get into the
new reporting options available for traces in Oracle 10g.
See All Articles by Columnist James Koopmann