PRVF-4664 PRVF-4657: Found inconsistent name resolution entries for SCAN name

APPLIES TO:

Oracle Database - Enterprise Edition - Version 11.2.0.1 to 11.2.0.3 [Release 11.2]
Information in this document applies to any platform.

PURPOSE

runInstaller (OUI) reports INS-20802 while running Oracle Cluster Verification Utility post check after successful 11gR2 Grid Infrastructure clusterware (CRS) installation or upgrade:

• Installation log - $ORACLE_BASE/oraInventory/logs/installActions{$TIMESTAMP}.log

INFO: PRVG-1101 : SCAN name "cluscan.us.oracle.com" failed to resolve
INFO: ERROR:
INFO: PRVF-4664 : Found inconsistent name resolution entries for  name "cluscan.us.oracle.com"
INFO: ERROR:
INFO: PRVF-4657 : Name resolution setup check for "scanclunm" (IP address: 10.4.0.202) failed

OR

PRCS-1016 : Failed to resolve Single Client Access Name cluscan.us.oracle.com

If "$GRID_HOME/bin/cluvfy comp scan" is executed, similar message will be reported.

DETAILS

 

Cause 1. SCAN name is expected to be resolved by local hosts file

SCAN name is resolved by local hosts file (/etc/hosts or %SystemRoot%\system32\drivers\etc\hosts) instead of DNS or 

Solution: Oracle strongly recommend to use DNS or GNS for SCAN name resolution as hosts file support only one IP for SCAN

If the intention is to use hosts file for SCAN name resolution, and ping command returns correct SCAN VIP, you can ignore the error and move forward.

If the intention is to use DNS or GNS for SCAN name resolution, comment out entries in local hosts file for SCAN name on all nodes, and re-run "$GRID_HOME/bin/cluvfy comp scan" to confirm.

 

Cause 2. nslookup fails to find record for SCAN name:

nslookup cluscan.us.oracle.com
..

** server can't find eotcs.us.eot.com: NXDOMAIN

Solution: Engage System Administrator(SA) to check resolver configuration (/etc/resolv.conf on Linux/UNIX), correct any misconfiguration on all nodes and re-run "$GRID_HOME/bin/cluvfy comp scan" to confirm.


Cause 3. SCAN name is canonical name(CNAME record) in DNS

nslookup cluscan.us.oracle.com
..
cluscan.us.oracle.com     canonical name = cluscan.a3.oracle.com
Name:   cluscan.a3.oracle.com
Address: 10.4.0.201
Name:   cluscan.a3.oracle.com
Address: 10.4.0.202
Name:   cluscan.a3.oracle.com
Address: 10.4.0.203

Solution: Engage SA to update SCAN record in DNS to A type instead of CNAME type.


Cause 4. DNS is configured properly in DNS but other naming resolution(nis, ldap..) is being used and doesn't have proper SCAN info

Solution: Engage SA to check name resolution switch configuration (/etc/nsswitch.conf on Linux, Solaris and hp-ux or /etc/netsvc.conf on AIX) and correct any misconfiguration on all nodes. Example hosts in nsswitch.conf:

hosts:      files dns nis

Once it's corrected, execute "$GRID_HOME/bin/cluvfy comp scan" to confirm


Cause 5. Persistent cache for nscd has incorrect information.

Solution: Engage SA to restart nscd and clear persistent cache on all nodes. Example on Linux

# /sbin/service nscd restart
# /usr/sbin/nscd --invalidate=hosts

Once it's corrected, execute "$GRID_HOME/bin/cluvfy comp scan" to confirm.

 

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What's the expected output when executing nslookup

nslookup cluscan.us.oracle.com

..
Name:   cluscan.us.oracle.com
Address: 10.4.0.201
Name:   cluscan.us.oracle.com
Address: 10.4.0.202
Name:   cluscan.us.oracle.com
Address: 10.4.0.203


ping -c 1 cluscan.us.oracle.com
PING cluscan.us.oracle.com (10.4.0.201) 56(84) bytes of data.
64 bytes from cluscan.us.oracle.com (10.4.0.201): icmp_seq=1 ttl=64 time=0.258 ms

--- cluscan.us.oracle.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.258/0.258/0.258/0.000 ms

ping -c 1 cluscan.us.oracle.com
PING cluscan.us.oracle.com (10.4.0.202) 56(84) bytes of data.
64 bytes from cluscan.us.oracle.com (10.4.0.202): icmp_seq=1 ttl=64 time=0.258 ms

--- cluscan.us.oracle.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.258/0.258/0.258/0.000 ms

ping -c 1 cluscan.us.oracle.com
PING cluscan.us.oracle.com (10.4.0.203) 56(84) bytes of data.
64 bytes from cluscan.us.oracle.com (10.4.0.203): icmp_seq=1 ttl=64 time=0.258 ms

--- cluscan.us.oracle.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.258/0.258/0.258/0.000 ms

From above you can see:

  1. nslookup is returning proper SCAN name and IPs
  2. ping to SCAN name is Round Robin resolved to different IP each time by DNS

If you see different behaviour than above, please engage SA to investigate.

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Ping command reference

 

Linux:        /bin/ping -c 1 cluscan.us.oracle.com
Solaris:      /usr/sbin/ping -s cluscan.us.oracle.com 1500 1
hp-ux:       /usr/sbin/ping cluscan.us.oracle.com -n 1
AIX:         /usr/sbin/ping -c 1 cluscan.us.oracle.com
Windows: ping -n 1 cluscan.us.oracle.com

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REFERENCES

 - CLUVFY PRVF-4664 : FOUND INCONSISTENT NAME RESOLUTION ENTRIES FOR SCAN NAME
NOTE:887522.1 - Grid Infrastructure Single Client Access Name (SCAN) Explained