Your database has archive logging enabled and RMAN backups are taken at regular intervals. A data file in the USERS tablespace is damaged. Which command must you execute before starting the recovery…

When a data file in a tablespace is damaged and recovery is necessary, the `ALTER TABLESPACE users OFFLINE` command must be executed. Taking the tablespace offline ensures that no new transactions can access or modify the tablespace, which is crucial for maintaining data consistency during the restoration and recovery process.

`STARTUP FORCE NOMOUNT` is used to start an instance without mounting a database, typically for database creation or specific RMAN operations, not for recovering an existing tablespace.

`STARTUP FORCE` is used to shut down and restart the instance, but it does not specifically prepare a tablespace for recovery; the tablespace still needs to be taken offline.

`SWITCH DATAFILE ALL` is an RMAN command used to change the location of data files during operations like switchover or copy, not as a prerequisite for initiating a tablespace recovery after damage.