question on "Alter Fragment on myTable attach"

Hello, I have an app running a "alter fragment on mytable attach ..." statement. Occasionally, this statement is launched while log_full.sh is running, so I get a SQL error -242, the corresponding ISAM error code is 106). I guess the reason is that "onbar -l" in ~informix/etc/log_full.sh locked up the database. Am I right ? I think IDS should support selecting waiting for a locked resource (table or index , etc) or returning an error immediately if the resource is locked, at SQL statement level. But I do not how to achieve this, is there anyone can give me a suggestion? Harry