I will be speaking at Austrian Oracle User Group event in Vienna this Wednesday (15. Oct) with Christian Antognini
I will deliver an 1 hour version of my Advanced Oracle Troubleshooting presentation there, so if you’re in Austria and want to see what’s coming in my full length seminar I deliver on 3.-4. Nov also in Vienna, then you can see a preview on this Wednesday :)
Whenever I deliver training or conference presentations on advanced troubleshooting topics, I usually spend some time demonstrating how to get and interpret Oracle server process stack traces.
As I’ve mentioned before, stack traces are the ultimate indicators showing where in Oracle kernel (or whatever application) code the execution currently is (or where it was when a crash occurred). This is the reason Oracle Support asks for stack traces whenever there’s a crash or non-trivial hang involved, that’s why Oracle database dumps errorstacks when ORA-600’s and other exceptions occur.
There are multiple ways for getting stack traces for Oracle, but not all ways are equal. Some give you more contextual info, some less, but what I’m blogging about today is that some ways are less safe than others.
I was using pstack on Linux for diagnosing an IO related performance issue. I executed a create table as select statement and ran pstack in a loop for getting stack traces from the running process.
However in one of the test runs I got following error in my Oracle session:
SQL> create table t as select * from dba_source;
create table t as select * from dba_source
*
ERROR at line 1:
ORA-01115: IO error reading block from file 1 (block # 11161)
ORA-01110: data file 1: '/u01/oradata/LIN10G/system01.dbf'
ORA-27091: unable to queue I/O
ORA-27072: File I/O error
Additional information: 3
Additional information: 11145
Additional information: 32768
I suspected that this issue was due Linux pstack, stopped the pstack script and ran my CTAS from the same Oracle session again:
There’s a nice Metalink Note 438452.1 about various less known Oracle performance tuning utilities.
If you haven’t heard about things like StackX, LTOM, HangFG, SQLTXPLAIN, OS_Watcher or OPDG then it’s time to check this note out! :)
Administration, Oracle, Performance, Tools, Troubleshooting, Uncategorized
In addition to Hotsos Symposium this week, I will deliver my Advanced Oracle Troubleshooting presentation and demos at NYOUG DBA SIG this Thursday (06. March 2008) in Oracle’s Park Avenue office in Manhattan, NYC. If you are interested, see the details at http://www.nyoug.org/upcoming_events.htm#dbaname
Also, I will be speaking at Trivadis Performance Days in Zurich 23.-24. April 2008. I will deliver the following presentations/demos:
If you are interested, visit this link:
https://www.trivadis.com/shop/Kursdetail.aspx?KategorieID=2&SubkategorieID=78&KurseID=608
If you work with Oracle databases and are interested in system performance, then you probably want to know what Cary Millsap has to say. So, make sure you bookmark his blog: http://carymillsap.blogspot.com/
This is a test posting, no real content here...
-bash-3.00$ pstack 868 868: ora_pmon_SOL01 fffffd7ffc7dddca pollsys (63726c0, 2, fffffd7fffdfdc90, 0) fffffd7ffc7845c2 poll () + 52 0000000004eb8bd0 ntevpque () + 60 0000000004eb66e6 ntevque () + b6 0000000004e93968 nsevwait () + 178 0000000001905453 ksnwait () + 63 00000000017b0cc7 ksliwat () + 8a7 00000000017b1425 kslwaitns () + 15 00000000018dd89f kskthbwt () + bf 00000000017b13ed kslwait () + 4d 00000000017ba502 ksuclnwt () + b2 00000000017ba8f7 ksucln () + 327 000000000184ecb5 ksbrdp () + 325 00000000028d3dd6 opirip () + 2a6 0000000000e76aea opidrv () + 3ba 0000000000e73e7b sou2o () + 5b 0000000000e3a86c opimai_real () + 11c 0000000000e3a6a4 main () + 64 0000000000e3a4ec ???????? ()
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