Host lost access to LUNs?

Anil,

Please consider moving this question as-is (no need to recreate) to the proper forum for maximum visibility.  Questions written to the users' own "Discussions" space don't get the same amount of attention and questions can go unanswered for a long time. 

You can do so by selecting "Move" under ACTIONS along the upper-right.  Then search for and select the array (based on your other post, is it a Symmetrix?) which would be the most relevant for this question.

Once the post is relocated, the army of dedicated customers, partners, and EMC employees eager to assist are surely going to need more information about your environment such as (but not limited to): array which will be generally answered once you relocate the post, PowerPath or native multi-pathing software, etc.

You may consider also in the meantime, opening up a ticket with support if you haven't already.

Hi Anil, Please mention you environment too.

although the basic troubleshooting revolves around verifying paths from the initiator till the target device. based on the environment you have,

you can check the status of the switch ports where your server's HBA is connected and also where the arrays front end ports are connected to.

Check the zoning on the switch for that respective server.

Check the status of the lun ont he array.

further comments possible only if you let us know the env and do the above.