Using the debugger
You can use Debug Tool to debug your Enterprise COBOL programs. Use the TEST compiler
option to prepare your COBOL program so that you can step through
the executable program with the debugger.
For remote debugging, there is an Eclipse plugin that provides a client graphical user interface to the debugging information provided by the Debug Tool engine running under z/OS® or z/OS UNIX. The IBM® Debug Tool Plug-in for Eclipse is included with IBM Developer for z/OS and also with the IBM Problem Determination Tools Studio.
You can specify the TEST suboption NOSOURCE to
have smaller object programs stored on disk. The loaded size does
not change, the debug information is never loaded unless requested,
for example, by a debugger such as Debug Tool or by LE (for CEEDUMP). 
With the NOSOURCE suboption, you will
not be able to see the source in the Debug Tool source window.
Specify the OPTIMIZE(0), NOSTGOPT and TEST compiler
options to get the most debugging function.
Specify a non-zero OPTIMIZE level, NOSTGOPT and TEST(EJPD) compiler
options to get better performance with a few restrictions on debugging
function.
Specify a non-zero OPTIMIZE level, STGOPT and TEST(NOEJPD) compiler
options to get the best performance but still be able to use Debug
Tool, with some restrictions on debugging function.
For details about which compiler
options to use for maximum debugging capability versus best performance,
see the related reference about the TEST compiler
option.
z/OS Debugger User's Guide (Preparing your program for debugging)