Hi Balaji, have you tried to use no_squash options?
Can you share with us the NFS options you're using? So we can compare it with the recommendations given in the installation guide.
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Please note that you should 'export' the sapmnt directory as described in the guide. For your reference, please download the guide at:
http://www.service.sap.com/sltoolset -> Software Logistic Toolset 1.0 -> [Scroll down the page] Software Provisioning Manager -> Installing Systems Based on NW 7.1 or Higher-SW Prov.Mgr.1.0
Please follow as descrined in section "5.3 Exporting and Mounting Global Directories".
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See also
http://help.sap.com/saphelp_nw70ehp2/helpdata/en/0a/0a2e39ef6211d3a6510000e835363f/frameset.htm
https://service.sap.com/sap/support/notes/2093132
Regards,
Americo