Call now: 252-767-6166  
Oracle Training Oracle Support Development Oracle Apps

 
 Home
 E-mail Us
 Oracle Articles


 Oracle Training
 Oracle Tips

 Oracle Forum
 Class Catalog


 Remote DBA
 Oracle Tuning
 Emergency 911
 RAC Support
 Apps Support
 Analysis
 Design
 Implementation
 Oracle Support


 SQL Tuning
 Security

 Oracle UNIX
 Oracle Linux
 Monitoring
 Remote s
upport
 Remote plans
 Remote
services
 Application Server

 Applications
 Oracle Forms
 Oracle Portal
 App Upgrades
 SQL Server
 Oracle Concepts
 Software Support

 Remote S
upport  
 Development  

 Implementation


 Consulting Staff
 Consulting Prices
 Help Wanted!

 


 Oracle Posters
 Oracle Books

 Oracle Scripts
 Ion
 Excel-DB  

Don Burleson Blog 


 

 

 


 

 

 
 

Fix Oracle Hanging

Oracle Tips by Burleson Consulting
February 4,  2009

Question:  I have an Oracle task that is hanging.  What causes Oracle to hang?  How can I detect the cause of an Oracle hang?  How do I fix an Oracle hang problem?

Answer:  Oracle hangs only when he is waiting for a resource.  It might be a latch (lock), or server resources (CPU, RAM). 

For more complete details on diagnosing a hung database, see the book "Advanced Oracle Utilities: The Definitive Reference".

Other possibilities for Oracle hanging include:

  • Pathing hang - Make sure that your Oracle environment variables are properly set ($ORACLE_HOME).

  • External hang - The network being down, Kerberos security issues, SSO or a firewall issue can cause an Oracle connection to hang.  One way to test this is to set sqlnet.authentication_services=(none) in your sqlnet.ora file and retry connecting.

  • Listener down/hanging - Start by checking the listener (check lsnrctl stat).  Also, see my notes on diagnosing Oracle network connectivity issues.

  • RAM shortage hang - Over allocation of server resources, usually RAM, whereby there is not enough RAM to spawn another connection to Oracle.

  • Data hanging - It is not uncommon for an end-user session to “hang” when they are trying to grab a shared data resource that is held by another end-user.

Debugging a hung database

Back in Oracle 10g a hung database was a real problem, especially if the DBA could not connect via SQL*Plus to release the source of the hanging.  In these cases, the DBA had few options other than to force-down the instance and warmstart it.

There is a new feature in Oracle 11g SQL*Plus called the “prelim” option. This option is very useful for running oradebug and other utilities that do not require a real connection to the database.

root> sqlplus –prelim

SQL>

or

SQL> set _prelim on

SQL> connect / as sysdba

At this point you are free to run the oradebug commands to diagnose a hung database issue using the new hanganalyze utility:

  1. SQL> oradebug hanganalyze 3
  2. Wait at least 2 minutes to give time to identify process state changes.
  3. SQL> oradebug hanganalyze 3
  4. Open a separate SQL session and immediately generate a system state dump.
  5. SQL> alter session set events 'immediate trace name SYSTEMSTATE level 10';

You can also gat a trace dump to identify hung session details in Oracle Real Application Clusters (RAC) as follows:

  1. SQL> oradebug setmypid
  2. SQL> oradebug setinst all
  3. SQL> oradebug -g def hanganalyze 3
  4. ... Wait at least 2 minutes to give time to identify process state changes.
  5. SQL> oradebug -g def hanganalyze 3

There are several other ways to find the root cause of an Oracle hanging issue:

  • Automatic Session History - Check ASH during the hang (if you have purchased the license):

  • Report - Run a couple of STATSPACK or AWR snapshot during the hang and get an elapsed time report.

  • Check for locking - Whenever Oracle is has a session hangs waiting on a resource, this information can be found in the v$session view in the row_wait_file# and row_wait_block#. 

Column host format a6;
Column username format a10;
Column os_user format a8;
Column program format a30;
Column tsname format a12;
 
select
   b.machine host,
   b.username username,
   b.server,
   b.osuser os_user,
   b.program program,
   a.tablespace_name ts_name,
   row_wait_file# file_nbr,
   row_wait_block# block_nbr,
   c.owner,
   c.segment_name,
   c.segment_type
from
   dba_data_files a,
   v$session      b,
   dba_extents    c
see code depot for full scripts
where
b.row_wait_file# = a.file_id
and
c.file_id = row_wait_file#
and
row_wait_block# between c.block_id and c.block_id + c.blocks - 1
and
row_wait_file# <> 0
and
type='USER';

See these related notes on fixing Oracle hang issues:

  1. SQL hanging on TEMP space usage

  2. Fix hanging SHUTDOWN: waiting for active calls to complete

  3. SQL*Plus hangs

  4. Export "hangs" while exporting definitions

  5. Oracle hangs and you cannot connect

 

 


 

 

��  
 
 
 
 

 
 
 

 
 
Oracle performance tuning software 
 
oracle dba poster
Oracle Linux poster
 
 

 

Burleson is the American Team

Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

Verify experience! Anyone considering using the services of an Oracle support expert should independently investigate their credentials and experience, and not rely on advertisements and self-proclaimed expertise. All legitimate Oracle experts publish their Oracle qualifications.

Errata?  Oracle technology is changing and we strive to update our BC Oracle support information.  If you find an error or have a suggestion for improving our content, we would appreciate your feedback.  Just  e-mail:  and include the URL for the page.


                    









Burleson Consulting

The Oracle of Database Support

Oracle Performance Tuning

Remote DBA Services


 

Copyright ? 1996 -  2014

All rights reserved by Burleson

Oracle ? is the registered trademark of Oracle Corporation.