There could be many cases that throw PRKO-2002, this is only a case when we tried to open the database to READ ONLY.
[oracle@primary01 ~]$ srvctl start database -d orclcdb -o read only
PRKO-2002 : Invalid command line option: only
PRKO-2002 means that an unknown option is found in the command, which is not a valid one. You should remove or correct it.
In fact, any srvctl commands using unmatched options always result in failure with PRKO-2002. You can list all possible combination by adding -h to look up:
[oracle@primary01 ]$ srvctl start database -h
Starts the database.
Usage: srvctl start database -db <db_unique_name> [-startoption <start_options>] [-startconcurrency <start_concurrency>] [-node <node> | -serverpool "<serverpool_list>"] [-eval] [-verbose]
-db <db_unique_name> Unique name for the database
-startoption <start_options> Options to startup command (e.g. OPEN, MOUNT, or "READ ONLY")
-startconcurrency <start_concurrency> Number of instances to be started simultaneously (or 0 for empty start_concurrency value)
-node <node> Node on which to start the database
-serverpool "<serverpool_list>" Comma separated list of database server pool names
-eval Evaluates the effects of event without making any changes to the system
-verbose Verbose output
-help Print usage
To open the database to READ ONLY, you should use double quotation marks to wrap the phrase.
[oracle@primary01 ~]$ srvctl start database -d orclcdb -o "read only"
With quotation marks, Oracle takes the value as a whole to open the database.