I tried the Dash Top script and below result from that clearly showing the
top consumer as 'oauth' session. I am not able to see any rows from
v$db_object_cache when passing the P1 as filter to hash_value column, maybe
they must have been flushed away. Can this be some kind of buggy behavior?
TotalSeconds AAS %This EVENT TOP_LEVEL_CALL_NAME SQL_OPNAME P1TEXT P1
FIRST_SEEN LAST_SEEN
92480 77.1 72% library cache lock OAUTH handle address 1.28E+11 24-10-2021
22:25 24-10-2021 22:39
14560 12.1 11% SQL*Net message from dblink V8 Bundled Exec SELECT driver id
6.76E+08 24-10-2021 22:20 24-10-2021 22:39
4390 3.7 3% V8 Bundled Exec SELECT driver id 6.76E+08 24-10-2021
22:20 24-10-2021
22:39
820 0.7 1% OAUTH handle address 1.28E+11 24-10-2021 22:25 24-10-2021
22:39
780 0.6 1% VERSION2 SELECT cellhash# 1.61E+09 24-10-2021 22:20 24-10-2021
22:26
On Tue, Oct 26, 2021 at 1:18 AM Pap <oracle.developer35@xxxxxxxxx> wrote:
Thank You Mark. got it now.
Now as we are still trying to find what exact changes were made by the dev
team. I tried capturing the Dash Wait chain using tanels scripts. And
attached are the results. The top sessions seem to be from 'jdbc thin
client' but from SYS , so I'm wondering if these are just from the OEM
tool. And this might be the victim but not the culprit. And the application
queries which were blocked with event = 'library cache lock' were showing
in_parse and in_hardparse column as 'N' , so means they were not getting
parsed while experiencing 'library cache lock'.
However, while I was manually trying to travel through the wait chain, I
saw its ending at some session with top_level_call_name as 'OAUTH'. and it
was executing the below query and then might be some 'alter user' from that
session. And because of sampling , it has not captured all statements
though. But we see the number of sessions with top_level_call_name as
'OAUTH' has been increased from <10 per hour to ~40K+ in an hour during the
issue period. So can it be the cause or is it the victim of some other ?
How should we proceed to get to the cause? And if it's a good idea to bump
the shard_pool size here?
select exptime, ltime, astatus, lcount from user$ where user#=:1
On Tue, Oct 26, 2021 at 12:19 AM Mark W. Farnham <mwf@xxxxxxxx> wrote:
dc_users is being modified by alter user. any parse needs to check
dc_users for what that user is allowed and where to put things like temp.
consistency is protected by a latch.
Is that the answer to your question about how it is logically related?
mwf
*From:* Pap [mailto:oracle.developer35@xxxxxxxxx]
*Sent:* Monday, October 25, 2021 12:22 PM
*To:* Mark W. Farnham
*Cc:* Oracle L
*Subject:* Re: Question on concurrency waits
Thank You Mark. So we are trying to reach out to the Dev team because it
seems to be fired from the application user as we can see from the user_id
column in v$active_session_history. But unfortunately the exact sql_text we
are not able to see from the database side.
And regarding the relation of library cache lock+cache cache lock with
the alter user, Would you explain a bit , how logically this is related. Is
this because each application query must be getting hard parsed , if the
underlying user from which it's fired is getting altered or anything else?
On Mon, Oct 25, 2021 at 9:30 PM Mark W. Farnham <mwf@xxxxxxxx> wrote:
yes, and the immediate question is to find out why alter user is being
issued.
*From:* oracle-l-bounce@xxxxxxxxxxxxx [mailto:
oracle-l-bounce@xxxxxxxxxxxxx] *On Behalf Of *Pap
*Sent:* Monday, October 25, 2021 6:31 AM
*To:* Oracle L
*Subject:* Re: Question on concurrency waits
My mistake, one correction:- the cache_id for all those 'row cache lock'
is pointing to dc_users.
On Mon, Oct 25, 2021 at 3:12 PM Pap <oracle.developer35@xxxxxxxxx> wrote:
Hi, It's 11.2.0.4 Oracle database. We are suddenly seeing many
application sql queries running slow and are showing 'library cache lock'.
And checking the ASH for the exact time period when the issue started and
the wait event appeared, we found few SYS sessions were doing 'ALTER USER'
from program 'passchng.exe' and we are not able to see exact statement from
sql_text for this (which may be because of its DDL and for DDL the AWR
doesn't capture the text as of 11.2.0.4). So I wanted to understand if the
ALTER USER command can cause such locking issues?
And also I see in the initial few minutes this session(Alter user
session) was showing 'library cache lock' and I don't know how to get more
information from the value of "handle address" but after some time, that
session was showing the 'row cache lock' with cache_id pointing to the
below cache objects. Are these can cause concurrency / "library cache lock"
for other application queries?
kqlsubheap_object
extensible security user and rol
extensible security principal pa
extensible security UID to princ
extensible security principal na
extensible security principal ne
XS security class privilege
qmtmrctp_cache_entries
qmtmrciq_cache_entries
