You can use Qcmdexc procedure from Sql without the command length parameter
Example :
Exec Sql Call Qsys2.Qcmdexc(‘Addlible Mylib’);
If you are using a variable for the command, you can use it like below:
CmdString = ‘Addlible Mylib’;
Exec Sql Call Qsys2.Qcmdexc(:CmdString);