If you do not want the plugin to update the server side 'have' database, check this box.

Typically Perforce keeps track of which files each client has synced down. This isn't always required, and in some cases may prevent the plugin from syncing at all (such as read-only/replicated servers). Enabling this option is equivalent to adding the '-p' flag to the sync command.

From the Perforce documentation: Populate a client workspace, but do not update the have list. Any file that is already synced or opened is bypassed with a warning message. This option is typically used for workspaces used in processes (such as certain build or publication environments) where there is no need to track the state of the workspace after it has first been synced. See the rest of the doc here: here.

Note: For whatever reason, perforce has decided that the -p option needs to be mutually exclusive of the -f option (even though they are functionally unrelated). As a result, you can't force sync and use -p at the same time. If you need to do a full resync while using the -p option, it's recommended that you delete the perforce client and let the plugin recreate it (assuming you are allowing it to manage the client workspace).