Hi Arun,
At SRO we have developed tools to overcome these kinds of issues. Our SDU tool eliminates lengthy downtime during upgrades by acting as a data transfer between the two environments. As an ex-customer we used it at my old company and our downtime from 7.5 -> 7.6 was under 5 minutes. Link is below but if you have any questions or want to chat let me know.
https://www.srosolutions.net/sdu-data-utility/------------------------------
David Shaw
Consultant
SRO Solutions
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