Log in to the specified instance by sqlplus under multiple oracle instances of windows
When multiple oracle services are installed under Windows, the system will set the database instance installed last time by default. To switch instances to log in sqlplus, modify the value of ORACLE_SID (set ORACLE_SID=xxxx, which is valid only for the current CMD window) in CMD window, and then access the database with the same CMD window.
Linux Settings.bash_profile
or temporary modification, export ORACLE_SID=ORCL;
