ORA-01801 date format is too long for internal buffer

I am using this function in my store procedure  to_char(sysdate,'yyyy/mm/dd hh24:mi:ss') usually it works fine, but sometimes it fails and the error message is:
ORA-01801 date format is too long for internal buffer How can this happen, Can I adjust the internal buffer?What should I do for it?

sheldon

• Sent from RemarQ http://www.remarq.com The Internet's Discussion Network * The fastest and easiest way to search and participate in Usenet - Free!