Sqlplus is prohibited in Oracle db.

Sqlplus is prohibited in Oracle db.

Record it first:

How to Disable a SQL * Plus Connection for a User (Documentation ID 124121.1)

Use the sqlplus/nolog command in the DOS window to log on to oracle. The result is similar to "sqlplus is not an internal or external command". What should I do?

Possible causes:
1. The oralce client is not correctly installed;
2. After installing oralce, the directory PATH registered to the system is lost in the PATH variable.

There will be no other reason.

Oracle creates a new database testdb, which can be connected using SQL plus, but cannot be logged on using PLSQL

After entering the PLSQL interface without logging in, click the above menu: Tools -- preferences. The following window is displayed.

Set your oracle Home directory in the red circle, and then re-open PLSQL, database column: testdb
This should be done.