I need to change package variable using JDBC and get new value back.
When I do it via java.sql.Connection, it returns new value of variable – 345:

    BigDecimal newValue = BigDecimal.valueOf(345);
    
    try (Connection conn = JDBCDataSource.getConnection()) {
        try (CallableStatement stmt = conn.prepareCall("{ call test_pkg.test_num := ? }")) {
            stmt.setBigDecimal(1, newValue);
            stmt.executeUpdate();
            conn.commit();
        }
    }

    BigDecimal retVal;
    
    try (Connection conn = JDBCDataSource.getConnection()) {
        try (CallableStatement stmt = conn.prepareCall("{? = call test_pkg.test_num}")) {
            stmt.registerOutParameter(1, Types.DECIMAL);
            stmt.executeUpdate();
            retVal = stmt.getBigDecimal(1);
            
        }
    }

    System.out.println(retVal);

But if unwrap java.sql.Connection to oracle.jdbc.OracleConnection using conn.unwrap(OracleConnection.class)
then it returns original value, not the new one.

I need to understand why it works in such way with OracleConnection and how to resolve it.