Hi Abhishek,
when you want to have r/w on S-Vol after a DR-Test, means you want to simulate Powering-Off the P-Vol site ?
See : https://knowledge.hitachivantara.com/Documents/Management_Software/SVOS/9.8.5/Global-Active_Device/11_Planned_outage_of_global-active_device_storage_systems
Section : Planned power off/on: primary storage system
Means, all the server I/O goes to the secondary storage system.
When you direct the server I/O only to the secondary site and split/suspend the GAD pairs (pairsplit -RS) then the S-Vol has the lastet data.
No extra flush step needed.
regards
Sven