Oracle DBA Daily Experiences

In v$session the column last_call_et has value which tells us the last time (seconds) ago when the session performed any activity within the database.

select username, floor(last_call_et / 60) "Minutes", status
from v$session
where username is not null — to ignore background process
order by last_call_et;

USERNAME Minutes STATUS
—————————— ———- ——–
SYS 0 ACTIVE
SCOTT 0 INACTIVE
SYSTEM 34 INACTIVE
..

Explain plan may not relay the correct execution plan optimizer may run, the following link shows an example
Explain Plan Lies

Using the following script it will find all version of a command in $PATH (from Unix Power Tools)

$ cat /tmp/whereiz
#!/bin/sh
testx="test -x"

fixpath="`echo $PATH | sed \
-e 's/^:/.:/' \
-e 's/::/:.:/g' \
-e 's/:$/:./'`"

# echo $fixpath
# IFS has a colon, space and a tab
IFS=": "
for command
do
where=""
for direc in $fixpath
do $testx $direc/$command && where="$where $direc/$command"
done
case "$where" in
?*) echo $where ;;
esac
done

Example
$ /tmp/whereiz ls grep
/bin/ls /tmp/ls
/bin/grep

By setting trap one can run a logout script when a k-shell is being terminated. The built-in command trap in k-shell allows one to customize shell when a signal is received.

# Set to run $HOME/.logout script when shell is terminated
$ trap ‘. $HOME/.logout’ 0
# display list of signals setup
$ trap
trap — ‘. $HOME/.logout’ EXIT

Run the following SQL to find permissions granted on users on the database

select
case when p.protecttype = 205 then 'GRANT'
when p.protecttype = 206 then 'DENY'
else 'unknown'
end + ' ' +
case when p.action = 193 then 'SELECT'
when p.action = 197 then 'UPDATE'
when p.action = 195 then 'INSERT'
when p.action = 196 then 'DELETE'
when p.action = 224 then 'EXECUTE'
else 'unknown'
end + ' ON ' + objectowner.name + '.' + o.NAME + ' TO ' + u.name
from sysusers u
inner join sysprotects p on u.uid = p.uid
inner join sysobjects o on o.id = p.id
inner join sysusers objectowner on o.uid = objectowner.uid
WHERE u.name = 'username'
order by o.name, u.name

From the following KB article it list couple of store procedures which can be used to send email through SQLServer. One of the feature it has the “From/Sender” can be passed in a parameter where as in case xp_sendmail it can’t be.
http://support.microsoft.com/kb/312839

Using “oradebug dump errorstack <dump level>” one can dump the call stack of the process after attaching to a running session. There are 3 values that can be passed as dump level
0 – dump error buffer
1 – level 0 with call stack
2 – level 1 with process state
3 – level 2 with context area

Example:
– Attach to a process
SQL> oradebug setospid 21906;
Oracle pid: 17, Unix process pid: 21906, image: oracle@localhost.localdomain (TNS V1-V3)
SQL> oradebug dump errorstack 3;
Statement processed.
SQL> oradebug tracefile_name;
/u01/oradata/admin/TEST/udump/test_ora_21906.trc

Information in the trace file:
…
*** 2010-07-22 21:35:56.554
*** SERVICE NAME:(SYS$USERS) 2010-07-22 21:35:56.554
*** SESSION ID:(27.1875) 2010-07-22 21:35:56.554
Received ORADEBUG command ‘dump errorstack 3′ from process Unix process pid: 22990, image:
*** 2010-07-22 21:35:56.554
ksedmp: internal or fatal error
—– Call Stack Trace —–
calling call entry argument values in hex
location type point (? means dubious value)
——————– ——– ——————– —————————-
Cannot find symbol
Cannot find symbol
Cannot find symbol
ksedst()+31 call ksedst1() 000000001 ? 000000001 ?
000000000 ? 000000000 ?
000000000 ? 000000001 ?
ksedmp()+610 call ksedst() 000000001 ? 000000001 ?

..

Using “oradebug dump events 1″ one can find/list events set in a session.

For example:
In a session events 10046 and 1410 events are set
SQL> ALTER SESSION SET EVENTS='10046 trace name context forever, level 12';

Session altered.

SQL> ALTER SESSION SET EVENTS='1410 trace name context forever, level 12';

Session altered.

In another session login as an account as sysdba
SQL> oradebug setorapid 12
Unix process pid: 10932, image: oracle@localhost.localdomain (TNS V1-V3)

SQL> oradebug dump events 1
Statement processed.

SQL> oradebug tracefile_name
/u01/oradata/admin/TEST/udump/test_ora_10932.trc

After running the above oradebug will dump the events in the trace file in the above case /u01/oradata/admin/TEST/udump/test_ora_10932.trc shows event 1410 and 10046 events set.
…
Dump event group for level SESSION
TC Addr Evt#(b10) Action TR Addr Arm Life
974FED50 1410 1 974fede0 0 0
TR Name TR level TR address TR arm TR life TR type
CONTEXT 12 0 -1 2 0
974FEBF8 10046 1 974fec88 0 0
TR Name TR level TR address TR arm TR life TR type
CONTEXT 12 0 -1 2 0
*** 2010-07-15 23:40:05.671
..

Suspend a running process
SQL> oradebug setorapid 12
Unix process pid: 10932, image: oracle@localhost.localdomain (TNS V1-V3)
SQL> oradebug suspend
Statement processed.

Resume a process
SQL> oradebug resume
Statement processed.

If you have trace turned on a suspended and resume session you will see the following messages in the trace file.
FETCH #5:c=54992,e=55962,p=0,cr=2334,cu=0,mis=0,r=1,dep=1,og=1,tim=1249098751175228
EXEC #5:c=0,e=72,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1249098751175408
Received ORADEBUG command ‘suspend’ from process Unix process pid: 22990, image:
*** 2010-07-13 21:12:34.268
Received ORADEBUG command ‘resume’ from process Unix process pid: 22990, image:
FETCH #5:c=58991,e=32316703,p=0,cr=2334,cu=0,mis=0,r=1,dep=1,og=1,tim=1249098783492125
EXEC #5:c=0,e=71,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1249098783492321

The following example shows how to set event on a oracle session

To turn on event, needs to be run as sysdba
SQL> connect /as sysdba
– attach to session by OS process id
SQL> oradebug setospid 5243378;
Oracle pid: 68, Unix process pid: 5243378, image: oracle@hostname (TNS V1-V3)
– sets maximum dump file size to be unlimited
SQL> oradebug unlimit
Statement processed.
– turn trace on
SQL> oradebug event 10046 trace name context forever,level 12
Statement processed.

To turn off event
– after gathering information from the same session which is already attached to ospid 5243378 turn off the trace
SQL> oradebug event 10046 trace name context off
Statement processed.

List of events can be found in $ORACLE_HOME/rdbms/mesg/oraus.msg