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Question and Answer

Connor McDonald

Thanks for the question, Sandeep.

Asked: May 01, 2016 - 1:14 pm UTC

Last updated: May 04, 2016 - 11:35 am UTC

Version: 11.2.0.4.0

Viewed 10K+ times! This question is

You Asked

Hi Tom,

Considering the arrangement of managing shared memory automatically, could you please help clarifying the below.

For 10g it was ASMM, For 11g it was AMM, So what is it there in 12c?
What are the benefits of AMM over ASMM [between 10g and 11g]?
What are the shortcomings present in ASMM, which are mitigated by AMM?
And how different it is in case of 12c?
Which shortcomings are addressed by 12c, which are present in 11g?
What additional features are included in 12c?

Thanks and Regards,
Sandeep

and Connor said...

The main difference was

ASMM - sga and pga were still separate.

AMM - sga/pga managed as one (so for example, you could shrink the pga to gain more sga etc).

I'm unaware of any significant changes to AMM in 12c (I'm sure there has been some changes/enhancements/fixes to the algorithms.

To my knowledge, AMM and hugepages are still not compatible...and hence, generally I've steered clear of AMM for that reason. I approach these facilities like this:

If I'm looking after 100 databases, probably 10 of them are "mission critical" in terms of importance, availability, performance etc. I'll probably use manual settings on these, because I'll be very proactive in monitoring them etc. For the other 90, which are less important, I'll probably turn on AMM and not worry about the minutiae.

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Comments

Sandeep Mishra, May 02, 2016 - 8:56 am UTC

Hi Connor,

Thank you.

Why cant I have ASMM for the 10 "Mission Critical" databases?
If neither ASMM nor AMM is reliable enough for a mission critical database, why create such designs?
And what benefit I will not have if I use ASMM, and the same benefit I get in Manual approach?

Thanks and Regards,
Sandeep
Connor McDonald
May 02, 2016 - 12:07 pm UTC

I didnt say not reliable enough. I said that if

a) you sit and monitor your database very actively, *and*
b) you know your applications, *and*
c) you know your business priorities

then it would make sense that you can tune almost any part of the database (including memory) better than the automated facilities can, because you have *more* knowledge of your apps, your data, your organization than the database ever will.

But do I want to sit and watch all 100 of my databases all day long, when (perhaps) 90 of them could even be down and no-one would notice (and I know *lots* of databases like that :-)).

Sandeep Mishra, May 04, 2016 - 9:07 am UTC

Hi Connor,

Thank You.

Let me enable ASMM
Let me monitor
Let me set individual parameters, so as per my knowledge the size specified, will be consider as a minimum to start with, and as the auto allotment is enabled, it can go to a higher value if required.

Without considering the forgetfulness of human mind . J
To me the above approach sounds better, rather than simply disabling ASMM and making everything static. Would be much happy to be corrected.

Thanks and Regards,
Sandeep
Connor McDonald
May 04, 2016 - 11:35 am UTC

I agree.
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