Oracle 10g Release 2 CSS parameters
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Oracle Database 10g Release 2 CSS (Cluster Synchronization Service) parameters:
With different patch-sets of Oracle Database 10g Release 2; there exist different timeout parameters which are used by CSS while accessing storage data. In this document we will cover following Oracle Database 10g Release 2 patch-set versions:
1. Oracle Database 10.2.0.1
2. Oracle Database 10.2.0.1 + Patch for Bug 4896338
3. Oracle Database 10.2.0.2
4. Oracle Database 10.2.0.3
1. Oracle Database 10.2.0.1
There is only one CSS parameter available in this version of Oracle and it is called misscount which represents the maximum time in seconds that, a heartbeat can be missed before entering into cluster reconfiguration to evict the node, and the maximum time allowed for a voting file I/O to complete.
The default value for misscount is 60 seconds.
2. Oracle Database 10.2.0.1 + Patch 4896338 and Oracle Database 10.2.0.2
There is bug 4896338 with Oracle Database 10.2.0.1 which is a placeholder bug for PCW 10.2.0.1 merge for very low brownout. Please refer
www.metalink.oracle.com for more details.
Oracle Database 10.2.0.2 has a fix for this bug.
There are three CSS parameters available in 10.2.0.2 and 10.2.0.1 + patch for bug 4896338; they are as follows:
a) misscount - It represents maximum time in seconds that, a heartbeat can be missed before entering into a cluster reconfiguration to evict the node.
b) disktimeout - It is the maximum amount of time allowed for a voting file I/O to complete; if this time is exceeded the voting disk will be marked as offline.
c) reboottime - It is the amount of time allowed for a node to complete a reboot after the CSS daemon has been evicted.
Default values for these parameters are as follows:
misscount = 60 seconds
disktimeout = 200 seconds
reboottime = 3 seconds
Using “crsctl get css disktimeout / reboottime” will not show parameter value unless you modify it explicitly. You can check the parameter’s values using ocssd.log under $CRS_HOME directory. 8
CRS internally calculates two parameters namely diskshorttimeout and disklongtimeout (can be checked in ocssd.log), where
a) diskshorttimeout = misscount - reboottime : This value is used during reconfiguration and initial cluster formation as a timeout for voting file I/O to complete.
b) disklongtimeout = disktimeout : This value is used during normal operation of RAC as a timeout for voting file I/O to complete.
3. Oracle Database 10.2.0.3
This version also has same parameters as that of Oracle Database 10.2.0.2; also the default values are same as Oracle Database 10.2.0.2. There is slight difference in the internal calculation of there parameter values; If disktimeout is less than the misscount value then during cluster formation and throughout cluster operation misscount - reboottime is considered as disktimeout and the modified parameter disktimeout is ignored.
That is in Oracle Database 10.2.0.3 diskshorttimeout = disklongtimeout if css disktimeout parameter is less than css misscount.
4. Recommendations for Oracle Database 10g Release 2 CSS parameter values to be used with NetApp storage:
As diskshorttimeout = misscount - reboottime; and if misscount & reboottime are kept as default values i.e. 60 seconds & 3 seconds respectively; the time for accessing voting file will be considered as 57 seconds by CSS, so If the reconfiguration happens during the NetApp Storage takeover or giveback process there are chances of CRS reboot taking place; hence following are the recommended values for CSS timeout parameters for Oracle Database 10g Release 2 RAC to work smoothly during NetApp Storage takeover and giveback process.
1. Oracle Database 10.2.0.1
misscount = 120 seconds (default is 60 seconds)
2. Oracle Database 10.2.0.1 + Patch for Bug 4896338
misscount = 120 seconds (default is 60 seconds)
disktimeout = 200 seconds (default)
reboottime = 3 seconds (default)
3. Oracle Database 10.2.0.2
misscount = 120 seconds (default is 60 seconds)
disktimeout = 200 seconds (default)
reboottime = 3 seconds (default)
4. Oracle Database 10.2.0.3
misscount = 120 seconds (default is 60 seconds)
disktimeout = 200 seconds (default)
reboottime = 3 seconds (default)
All the above recommendations are for Linux Operating system.
Note: The stock version of Oracle database 10g Release 2 lower than 10.2.0.2 do not provide all the configurable CSS parameters; hence it is advisable to upgrade Oracle Database to 10.2.0.2 or higher.
Appendix
Commands to check / modify CSS parameters:
1. crsctl get css misscount ———- to check misscount value
2. crsctl get css disktimeout ——— to check disktimeout value
3. crsctl get css reboottime ———- to check reboottime value
4. crsctl set css misscount 120 ——— to set misscount to 120 seconds
5. crsctl set css disktimeout 200 ——- to set disktimeout to 200 seconds
6. crsctl set css reboottime 3 ———– to set reboottime to 3 seconds
