Hi @chandana sasi ,
As per my knowledge, this is a normal scenario and I'm afraid there is no way to overcome it. SPMT is just a migration solution, it doesn't support building a synchronization between your local file share and SharePoint Online library. To sync SharePoint Online library with local file server, you can take other tools such as Azure file sync, OneDrive or some 3rd-party apps into consideration. A thread on this topic for your reference: Sharepoint Online and Local file server sync.
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