ISAM Error SQL error -243

Hello, I am hoping you cold help me. I have a program written in C with embedded SQL (CESL) code. In running the program, in one of the delete steps, I get an error SQL ERROR -243 SQL Message = [owner.tabname] ISAM error=[-113] ISAM error: the file is locked.I know that there are no other processes running simultaneously to have caused a lock on this table. What might have caused this issue?. The problem is if I run the program again, it rUNs fine.. Thanks, Jernand