An external C stored routine has the following characteristics:

• Absence of communication overhead between server and client
  As in the case of SQL stored procedures and SQL stored functions, external C stored routines are processed at the server, which eliminates communication overhead between server and client.
  
• Ability to code the procedure or function itself in C
  Because the C language instructions can be directly coded, processing can be coded more flexibly than with SQL control statements.
  
• Simple debugging
  The debugging of an SQL stored procedure or an SQL stored function requires actual execution at the server of the procedure or function. By contrast, external C stored routines can be debugged by providing a C language debugger at the client.