PL/SQL: Get max length of a varchar2 type

Below are the first lines of a procedure that shall write a log entry into a log table. It gets a string of variable length and than cuts it so it fits into the column. My problem: How to know the maximum size of the column? With %TYPE I get a variable of the corresponding type, but how to get its length?

PROCEDURE write_log(p_msg VARCHAR2) IS
  v_msg log_table.msg%TYPE;
  v_msg_maxlen og_table.msg%TYPE_LENGTH; -- does not exist, but maybe there is something alike?
BEGIN
  v_msg := SUBSTR(p_msg, 1, v_msg_maxlen);   ...

Simply assigning p_msg to v_msg would raise an overflow error, so I must know the max size for v_msg somehow and use substr as sketched in above code snippet. How can this problem be solved easily? I know I could write a query on all_tab_columns(?) and retrieve information on a database column, but this seems very much overhead, knowing that the information I seek is already inside my v_msg variable. I just don't know how to get it.

Thanks in advance,
Thorsten. Received on Fri Sep 14 2007 - 05:33:33 CDT