In case anyone needs a reminder, its always a good idea to determine the impact of your monitoring tools on the very database you are monitoring. Some monitoring tools are lightweight and others are more obtrusive. I am using Enterprise Manager 13c to monitor a specific SQL statement while its running. I noticed in another monitoring tool (Lighty by Orachrome) the following SQL statement was consuming a good amount of resources:
WITH MONITOR_DATA AS (
SELECT
INST_ID
,KEY
,NVL2 (
PX_QCSID
,NULL
,STATUS
) STATUS
,FIRST_REFRESH_TIME
,LAST_REFRESH_TIME
,REFRESH_COUNT
,PROCESS_NAME
,SID
,SQL_ID
,SQL_EXEC_START
…
I cut off the rest of the text. This SQL statement is literally a few thousand lines long. Yikes! But that isn’t the issue. In Lighty, I noticed the activity in this screen shot.
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The top SQL statement is my CPU pig. I blacked out the SQL text to protect potentially proprietary information. Notice that last SQL statement. It is consuming a fair amount of resources for just monitoring the system.
Here is a screenshot of the EM13c window.
When I turned off the Auto Refresh (it defaults to 15 seconds), the activity ceased on the system. I then manually press the refresh button when I need an update.
There are certainly times to use the auto refresh, even every 15 seconds. Just be mindful of the potential negative impact on the database.
