This document provides instructions on how to use HANGANALYZE and interpret HANGANALYZE trace files to diagnose hangs or lock waits in Oracle databases. It describes how to run HANGANALYZE on single node and RAC configurations, alternative diagnostic tools like HANGFG, and how to interpret the output files including identifying blocking sessions and chains.

1. How to use HANGANALYZE and How to
Interpreting HANGANALYZE trace file
Kamus@Enmo Tech

2. How to - Single Node
• sqlplus / as sysdba
• oradebug setmypid
• oradebug unlimit;
• oradebug hanganalyze 3
• ... wait at least 1 minute
• oradebug hanganalyze 3

3. How to - RAC
• sqlplus / as sysdba
• oradebug setmypid
• oradebug unlimit;
• oradebug setinst all
• oradebug -g def hanganalyze 3
• ... wait at least 1 minute
• oradebug -g def hanganalyze 3

4. How to - Using HANGFG
• MOS Note:362094.1
• RAC aware
• hangfg.sh 1|2|3
• default value is 2
• 1 is most light impact, hanganalyze level 3
• 3 is most heavy impact, hanganalyze level 4
• make sure you have “compress” cmd
• ln -s /bin/gzip /bin/compress

5. How to - If can’t login
• MOS Note: 121779.1
• sqlplus -prelim / as sysdba
• From Oracle 10g and Higher
• No session created, but limited access
to the SGA

6. How to - If can’t login
• MOS Note: 121779.1
• dbx
• Oracle 9i and earlier
• Source level debug
• Solaris, Linux

7. dbx
$ ps -ef|grep LOCAL
ora10g 28297 1 0 13:58 ? 00:00:00 oracleORCL (LOCAL=NO)
$ which dbx
/opt/oracle/solarisstudio12.3/bin/dbx
$ dbx
(dbx) attach 28297
(dbx) print ksdhng(3,1,0) *** oradebug hanganalyze 3
(dbx) print ksudss(10) *** oradebug dump systemstate 10
(dbx) print ksdsel(10046,12) *** 10046 trace level 12
(dbx) detach
(dbx) exit
$ cd /u01/app/oracle/admin/ORCL/udump
$ ls -lt | grep 28297
-rw-r-----. 1 ora10g oinstall 1427748 Dec 15 14:05 orcl_ora_28297.trc

8. How to - If can’t login
• MOS Note: 273324.1
• gdb
• Source level debug
• Linux, HP-UX

9. gdb
$ ps -ef|grep LOCAL
ora10g 28297 1 0 13:58 ? 00:00:00 oracleORCL (LOCAL=NO)
$ which gdb
/usr/bin/gdb
$ gdb $ORACLE_HOME/bin/oracle 28297
(gdb) print ksdhng(3,1,0)
(gdb) detach
(gdb) quit
$ cd /u01/app/oracle/admin/ORCL/udump
$ ls -lt | grep 28297
-rw-r-----. 1 ora10g oinstall 1427748 Dec 15 14:09 orcl_ora_28297.trc

10. Simulate row lock contention
• Session 1:
• update t set object_name='test' where
object_id=20;
• Session 2:
• update t set object_name='test1' where
object_id=20;
• Session 3:
• update t set object_name='test2' where
object_id=20;

11. Interpreting trace file
• Chains
• CYCLES
• BLOCKER OF MANY SESSIONS
• OPEN CHAINS
• OTHER CHAINS

12. Interpreting trace file
• State of Nodes
• IN_HANG
• LEAF / LEAF_NW
• NLEAF
• IGN / IGN_DMP
• SINGLE_NODE /
SINGLE_NODE_NW

13. Hanganalyze Level
• level 1-2
• only HANGANALYZE output, no process dump
• level 3
• [IN_HANG]
• level 4
• [REMOTE_WT] [LEAF] [LEAF_NW]
• level 5
• [SINGLE_NODE] [SINGLE_NODE_NW] [IGN_DMP]
• level 6
• [NLEAF]
• level 10
• [IGN]

14. Then?
• We got sid, serial#,ospid
• ps -ef| grep ospid
• v$session
• blocker -> sql_id, prev_sql_id,
logon_time
• waiter -> sql_id,
row_wait_obj#,blocking_session

15. If we don’t use hanganalyze
• v$lock
• v$locked_object
• v$enqueue_lock
• v$session / v$session_wait