Force users to use Active DG for reporting

We got an environment formed by one standalone 11g database (lets call it RW) with an active dataguard on another server (lets call it RO) We have provided to the users 2 tnsnames, one pointing to RW and the other to the RO, and we have told them to use the first one for DML, etc and the RO only for runing the reporting statments.

As good users, they just ignore us and run all on the RW database, so we want to force them to use the RO for reporting. Meanwhile they got the 2 tnsnames entries, i see no real options to force them to use the RW, unless we separate the schema in two (one with insert/update, the other only with select), and we kill any session of the select schema on the RO (using a cron maybe, forcing them to use RW to be able to end their reports)

Has any of you found in a similar situation, or can think in other options?

Thanks

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