Assuming you have enabled archival logging and have enough disk space ,
a) Create new instance
b) Online Backup database on old
c) Restore database on new, but leave rollforward pending
d) Apply logs from old to new continually, leaving the new in pending state
e) Stop the old instance
f) Get the latest logs and apply it on new, and rollforward complete
If you wish the clients to access the database without any changes to their config, then change the SVCENAME of the new instance to same as old ...
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