An attempt was made to assign a server to the server pool that did not have the specified role. Only servers with the specified role can be assigned to this server pool.
Add more servers to the cluster, stop or relocate the resources mentioned right before this error, or reissue the command with the -force option.
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Try the following links for this error:
http://docs.oracle.com/cd/E16655_01/server.121/e26079/crsus.htm