standby database

There are two servers machines PROD & D.R. with OS Linux and database oracle Release 12.2.0.1.0

The PROD machine having three PROD Oracle instances, there SID name like PROD1, PROD2 and PROD3 and same SID exists on DR machine, which are standby database of PORD SID like PROD1, PROD2 and PROD3. My question while creating control file of standby database with below command

alter database create standby controlfile as '/contrlfileprod1.ctl';

alter database create standby controlfile as '/contrlfileprod2.ctl';

alter database create standby controlfile as '/contrlfileprod3.ctl';

 

Open their aler_log file like Alert_prod1.log, Alert_prod2.log, Alert_prod3.log,