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Connor McDonald

Thanks for the question, Sivasankar.

Asked: September 26, 2019 - 3:32 pm UTC

Last updated: October 01, 2019 - 1:05 am UTC

Version: 12.2.1.0

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You Asked

Hi,
The column TM_DELTA_TIME shows null value for some sessions even though the session is WAITING or onCPU when I query the view v$active_Session_history in oracle 12CR2.What does it indicate and When is the column NULL?Can TM_DELTA_TIME be more than 1 second which is the sample frequency for the view?

and Connor said...

TM_DELTA_TIME is designed not as a "row by row" piece of information, but in conjunction with the other two columns that partner it, TM_DELTA_CPU_TIME and TM_DELTA_DB_TIME

For example if you had:

TM_DELTA_TIME = 4,000,000
TM_DELTA_DB_TIME = 1,500,000
TM_DELTA_CPU_TIME = 1,000,000

then we interpret that as

"In the last 4 seconds, 1.5 seconds of that was time on the database, of which 1 second was CPU"

The session is active *now* (which is why it is in active session history), but the TM_DELTA.. columns are information about the session *life* as opposed to right now.

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One doubt

Sivasankar Mutnuri, September 27, 2019 - 11:45 am UTC

Then if TM_DELTA_TIME is Null , What does it mean or imply ?How to Interpret it?
Connor McDonald
October 01, 2019 - 1:05 am UTC

It means we did not have a measure for that particular moment. This is why it might be *more* than 1 second because it represents the time delta from the last time we took it.,
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