Chaitan,
Typically when I see this error message it means that when SnapCenter was installed the option to enable file indexing was not selected.
Without this the necessary components, including the API Server components, are not installed.
At this time the only solution is to uninstall and reinstall SnapCenter, making sure to select the index option during the install.
The index option is only avialable when using the MySQL database (since the API Server requires MySQL) and thus you cannot use the NLB or SQL Server repository options.
(note you can still backup SQL Server databases with SnapCenter, however SnapCenter's internal database must be MySQL and not SQL Server to use API Services).
John