PLS-00103: Encountered the symbol "：" when expecting one of the following:

This error message is usually encountered in Oracle PL/SQL and indicates that a symbol was found where it wasn't expected. The message suggests that the symbol "：" was encountered when expecting one of the following:

- A variable, constant or literal value
- A keyword such as IF, FOR, WHILE, etc.
- An operator such as +, -, *, /, etc.
- A closing bracket or parenthesis

To resolve this error, you need to carefully review your PL/SQL code and identify where the unexpected symbol was used. Check if it is a typo or if it violates the syntax rules of PL/SQL. Once you identify the issue, correct the code and try running it again.