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CRS & RACTroubleshooting

Krishnadev TelikicherlaCluster & Parallel Storage Technology

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Topics:

� Defining the Issue� Creating a Timeline� Hang or Slowdown� Performance Issues� Gathering Data� Testcases� Rediscovery� Engaging Oracle Support� Examples

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Defining the IssueLayers

� What layers are involved in the issue:

• Oracle Clusterware

• CRS daemon• CSS daemon• HangCheckTimer [Linux] / Oprocd (not

Linux)• EVM• OCR• Voting

• General RDBMS• Operating System• Hardware

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Defining the IssueCause vs. Effects

� Causes:– Resource issues– Oracle issues– OS issues

� Effects:– Hangs/Spins– Instances Crashes and Evictions– Node Reboots and Evictions– Oracle Errors (ORA-600, ORA-7445, ORA-29740)

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Defining the IssueDescription

� When describing the problem while creating the SR via Metalink it is important that you use phrases that will help identify known issues either in bugs or Metalink content.

� In the body of the SR try to be as detailed as possible about the environment.

� Nobody knows the system better than the you.� Talk to the sys-admin as well regarding OS/Network

related issues.

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Creating a Timeline

� A timeline helps identify the times to concentrate on when reviewing files

� A timeline can be built from reviewing the files themselves once they are provided to support but this will only slow resolution time down

� Timelines should include an ordering of cause and effects as well as include all participating nodes

� Include specific times, ie…– At 3:00am PST we noticed that node2 was hanging.

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Hang or slowdown

� Differentiate between a database hang and a database slowdown

� Identify the extent of a hang

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Is it a Hang or a Slowdown?

� Check:� System states to see if there is any change

over a short period of time� V$SESSION_WAIT where wait_time=0� Overall machine load, including cpu,

memory, swap, I/O

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Is it a Hang or a Slowdown?

� Single or multiprocess hang:– Usually characterized by a particular job

hanging or not completing– Essentially the same as in single instance

unless it’s internode parallel query.

� Instance hang: A single instance is unusable.

� Multi-instance or full database hang: Entire database is hung or not responding

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Performance

� Single process or statement� Instance� Multi-Instance

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Single Process or Single Statement� Find the wait event� 10046 level 12

- oradebug setorapid

- oradebug event 10046 trace name context forever, level 12- oradebug tracefile_name

� Explain plan� 10053 if plan problems are found� V$SESSTAT� Truss/trace/dbx/pstack if OS-related

problems are suspected

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Instance Slowdown

� Statspack / AWR� OS performance statistics - cpu, memory,

and I/O� Characteristics:

– Related to a particular job?– Certain time of day?– What’s changed?

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Multi-Instance Slowdowns

� AWR from each node can be of use:� AWR collects instance specific data� Examine and correlate the reports

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Multi-Instance Slowdowns

� In cases of extreme slowdowns:� systemstates on all nodes� V$SESSION_WAIT� Alert logs and any trace files� Process states, or stack traces if

determined and applicable

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Debugging Techniques

� v$session_wait� System states from all nodes� 10046 level 12 trace of the hung process� ORADEBUG� Lock layer and DLM tracing� Get any traces:

� DLM traces� Background processes, alert logs, and init.ora� User traces

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Debugging and Diagnostics

� Performance issues or hangs:� Identify the resource being requested.� Identify who holds the resource.

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ORADEBUG and Tools

� Hang analyze:– hanganalyze <level>

� Note: 301137.1 – OS Watcher User Guide� Note: 135714.1 - Script to Collect RAC

Diagnostic Information (diagcollection.pl)

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Gathering DataBest Practices

� Single most important step� There is never too much data, but including lots of

useless data can increase download time of the data as well as increase the amount of time to process the data.

� Always error on getting too much data, but be aware of the impact on the resolution time.

� Too little data increases resolution time more than too much data.

� Always include a readme.txt file that explains the contens of the provided files

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Gathering DataProcesses

� Always get stacks from processes that seem to be spinning, hanging or unresponsive:

– oradebug– gdb– pstack

� ps and top info can be very usefull when trying to determine if a processes exhibits issues such as memory leaks, spinning or hanging

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Gathering DataRAC

� For instance evictions please review Metalinknote 219361.1

� See Metalink note 203226.1 : RAC Survival Kit: Real Application Clusters Troubleshooting and Information

� See Metalink note 289690.1 : Data Gathering for Troubleshooting RAC and CRS issues

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Gathering DataTools

� RDA – system and Oracle configuration information� racdiag – modifiable sql script for gathering rac data. See

Metalink note 135714.1 “Script to Collect RAC Diagnostic Information

� OSW – OS Watcher gathers top, slabinfo, netstat and ps data over programmable intervals 301137.1 “OS Watcher User Guide”

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Gathering DataCRS 10.2.0.x (continued)

� CRS and other resource issues:– ORA_CRS_HOME

� log/<hostname>/cssd/oclsmon

� log/<hostname>/cssd

� log/<hostname>/client

� log/<hostname>/crsd

� log/<hostname>/evmd� log/<hostname>/racg

– ORACLE_HOME (rdbms)

� racg/dump

� ORACLE_BASE/<db_name>/hdump

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Gathering DataTools (continue)

� Starting with 10.2.0.1 $ORA_CRS_HOME/bin/diagcollection.pl collect all RAC relevant files (run as root)

oracle10@stnsp010>./diagcollection.plProduction Copyright 2004, 2005, Oracle. All rights reservedCluster Ready Services (CRS) diagnostic collection tooldiagcollection

--collect[--crs] For collecting crs diag information[--oh] For collecting oracle home diag information[--ob] For collecting oracle base diag information[--all] Default.For collecting all diag informationNOTE:1. You can also do the following

./diagcollection.pl --collect --crs --oh2. ORA_CRS_HOME,ORACLE_HOME and ORACLE_BASE env variables

need to be set.--clean cleans up the diagnosability

information gathered by this script--coreanalyze extracts information from core files

and stores it in a text file

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Testcases

� Not always feasible� If provided, can greatly influence resolution time� When providing a testcase:

– Include a readme file

– Try to strip the testcase down to the minimal elements that are needed to reproduce the problem

� If at all possible, always try to build a testcase� Testcases are your friends!

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Rediscovery

� Expensive for a support organization� Issue rediscovery is not always obvious� Use Metalink to identify possible causes for

issues as well as workarounds and patch availability

� Communicate new issues between DBAs

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Engaging Oracle Support

� Try to be responsive to all TARs when they are set to CUS status. Delays inherently causes two problems:1. The issue loses momentum2. A new engineer may have to take over the issue

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Examples

� 10.2.0.2 HP-UX/Itanium ServiceGuard, CRS, CFS and RAC

� Delays in reconfiguration

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Examples

� 10.2.0.2 Linux CRS, RAC and ASM� ORA-600[2103] and one instance crashed

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Questions?