RE: Memory needed for upgrade to 18c

From: Jeff Smith <>
Date: Sat, 18 May 2019 06:42:58 -0700 (PDT)
Message-ID: <523f29d5-4d6a-4fd6-b336-22455fd00b36_at_default>

Any chance this db is on AIX?

Herr Upgrade reminded me that there's a known bug for 12.1-12.2 upgrades that exhibit this behavior...could be it crept into 18c.

-----Original Message-----

From: Jonathan Lewis <> Sent: Saturday, May 18, 2019 5:29 AM
To:; Subject: Re: Memory needed for upgrade to 18c

What are you doing to check the memory usage of each instance ? Is this just the shared memory or are you doing something to include the actual memory usage of all the processes attached to the SGA as well ? Is the increase apparent from Oracle's perspective or is there something about Oracle's use of memory which has changed the way it's O/S memory pages that has led to more memory being allocated for the O/S memory map ? (Possible clues in the alert log if you've got old and new.)

You say 2GB more per instance - how much memory was each instance using before the upgrade (to give us some idea of the percentage increase). Do you have any record of memory allocation on startup for the databases you've upgraded - it's almost always the case that Oracle Corp. finds some new "overhead" to stuff into the code as you upgrade. 18c has

You say you have 22 single instances on that machine - are they all running separate virtual machines (please translate to AIX-equivalent terminology) or do you have many virtual machines with one (or more) instances per machine. (And can you tell us something about the total CPU count and memory of the hardware).

You say that the parameters are the same - but are you comparing all the parameters that you DIDN'T set that may have changed their default values. Again a comparison of old and new alert logs may help. As a quick check for large scale changes you could compare the before and after results of

select pool, sum(bytes) from v$sgastat group by pool order by 1;

This MIGHT highlight a significant change.

Jonathan Lewis

From: <> on behalf of Thanh NGUYEN <> Sent: 18 May 2019 08:17:52
Subject: Re: Memory needed for upgrade to 18c

Hello Stefan,

Thank you very much for your answer.

  1. We did not change any parameter related to memory. Furthermore, we got the same issue (memory usage increased), 2 years ago, when we upgraded from to
  2. We have 22 single instances at that server. It will take time if we determine the the consumption of each process.

Do you have any simpler idea?

Best regards,


$ ps -ef|wc

    3423 30419 238850
8:58:13 z004969:/users/ucib/z004969
$ ps -ef|grep smon|grep -v grep|wc

      22 198 1498

On 5/17/19 9:42 AM, Stefan Koehler wrote:

Hello Thanh,
ah AIX and Oracle is like Tom and Jerry ;-)

Maybe the good old "USLA heap" problem is back again. However if you have not changed any parameter (e.g. SGA_TARGET, MEMORY_TARGET, PGA_AGGREGATE_TARGET) and you are not using more (over-allocated) PGA than before than it is very likely caused by heap memory consumption of each Oracle process - you can check the memory and break it down with "svmon" very easily ( ).

Best Regards
Stefan Koehler

Independent Oracle performance consultant and researcher Website: Twitter: _at_OracleSK

Thanh NGUYEN <><> hat am 16. Mai 2019 um 21:31 geschrieben:

Aix 7.2 ML03
We upgraded 5 instances from to 18c, without changing any parameter. Then we observed that memory is used more than before the upgrade, nearly 2GB more for each. Do you have any experience/explanation about that please? Thank you in advance.
Best regards,



-- Received on Sat May 18 2019 - 15:42:58 CEST

Original text of this message