Thank you for the response.
As i mentioned we have 48 core CPU with 2 socket each for a node, so Total
~96 core per node. And the OEM also its showing showing the red line bar on
AAS as 96 as Max limit. But during three different issue period we see the
below AAS shoot ups above 96 and the wait distribution,
Basically its combination of wait event from classes like concurrency,
configuration and others but CPU part is minimum.
1) AAS shoot up to - 180, out of which 7% CPU and 34% (buffer busy waits),
~20% Log file switch checkpoint incomplete, 16% enq:tx allocate ITL entry,
12% Others.
2) AAS shoot up to - 515, out of which 4% CPU and 46% (library cache
lock), ~17% library cache mutex, 12% enq:tx allocate ITL entry entry, 12%
Others.
3) AAS shoot up to - 120, out of which 9% CPU and 30% (buffer busy waits),
~13% Log file switch checkpoint incomplete, 31% enq:tx allocate ITL entry
entry, 8% BCT buffer space.
But i think you are correct putting CAP on CPU using DB resource manager
may not going to help us in above situation as cpu portion is less than
10%. However, i was thinking if any possible way to put cap on the AAS or
the number of session those were spawning from the program prog_batch as
because they are the one causing the chaos by submitting lot many session
simultaneously. So is that possible with the DB resource manager
configuration or by tweaking the existing services in anyway?
Regards
Yudhi
On Wed, 22 Feb, 2023, 12:54 pm Ilmar Kerm, <ilmar.kerm@xxxxxxxxx> wrote:
Resource manager can help you if you are seeing resource shortage (CPU
shortage) during these periods and CPU shortage is causing the Concurrency
waits.
If you are not seeing CPU shortage, then you need traditional database
troubleshooting methods and resource manager will not help you.
For example if you are behind in 19c patching, then for example before
19.15 there was bug 32898678, 33541865 (fixed in 19.17) and multiple others
that caused block change tracking (BCT) to freeze the database or just high
BCT buffer space waits.
On Wed, Feb 22, 2023 at 6:08 AM yudhi s <learnerdatabase99@xxxxxxxxx>
wrote:
Thank you Andy.
I have never used the DB resource consumer group in our databases though.
But going through the doc, it seems it can be set for many number of input
parameters and also on many resources. Yet to test it , however In most
cases I see it's set on amount of cpu. So in our case will it be good idea
to determine the cpu percentage and define the plan or we can do it on
number of average active sessions which will be again hardcoded value only.
We need to set it for multiple input program values in our case. If you
can pass on reference to some sample doc with its exact code
implementation, that would be great.
On Wed, 22 Feb, 2023, 2:11 am Andy Sayer, <andysayer@xxxxxxxxx> wrote:
You can set up resource manager to map different programs to different
resource consumer groups. You’ll need to make sure you order the priority
of mapping to make sure program is checked before service name (if that’s
not the default). It’s all in dbms_resource_manager
Thanks,
Andy
On Tue, Feb 21, 2023 at 12:19 PM, yudhi s <learnerdatabase99@xxxxxxxxx>
wrote:
Hello Listers,
On a normal day, we see sessions/AAS per ~1 minute interval as ~50 in
this database. and they are mainly from two specific 'programs' (say e.g.
prog_batch, prog_online). But during certain periods of the day we saw a
large number of sessions with programs as 'prog_batch' (i.e. with AAS>~500)
flooding the database and we are seeing large concurrency waits, bct buffer
space waits all over the database. And its impacting critical sessions of
other programs i.e. prog_online. So considering 'prog_batch' is meant for
batch kind of processes and it's okay for those sessions to queue-up and
run a few minutes longer, but at the same time we can't afford to impact
the sessions from prog_online, as those are latency sensitive online users.
But we found both of these programs are pointing to the same database
services and running on the same node-1. So , apart from controlling the
number of sessions/connections from the application end, can we do some
easy fixes with regards to the service config level, which will better
control the incoming load? Or say putting some cap on the incoming sessions
from prog_batch?
This is a 19C database with 2 node RAC and its an Exadata machine. Each
node is a 48 core, 2 socket. Both the programs were using the same service
and having preferred nodes as node-1.
Regards
Yudhi
--
Ilmar Kerm
