JaswanthChadalawada4210560
Since you are saying policy and this blog is in CA SSO, i'll assume this to be CA SSO Policy Store.
I am not going to speak in any detail about "does dxloaddb command overwrites existing store"; because that is simply not the recommended approach for Policy Store. There is a difference between whether we can do it VS is it really the right approach. Our preference is to use the right / correct approach which ensure stability / continuity.
For Policy Store, it'd best if we use XPSTools (XPSExport and XPSImport) to do any policy migration. This will ensure any Policy Store object discrepancies or conflicts are handled by CA SSO XPS Tools.
If you do it using the DXTools and if there is any corruption. You risk the functioning of CA SSO Policy Server.
Regards
Hubert