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You can read more about the LOC here in this Ministry of Home Affairs site.
First point of this circular says
For the future, it is considered that whenever any authority issues a warning circular to the immigration authorities, the period of validity should be clearly specified in the circular. If this is not done, the circular will be considered to be valid only for a period of one year from the date of issue and a watch will be maintained by the person concerned at the immigration check posts only for that period.