1.) To enable cell trace with increased file size (the default is 25Mb with 11.3.03 and higher):
 
a) Modify MCELL_HOME/etc/<cell>/mcell.conf to contain:
Trace=Yes
TraceFileSize=50M
 
Each trace file will be maximum of 50Mb and there will be maximum of 10 files (default value for parameter TraceFileHistory). These numbers can be adjusted depending on how much free space there is.
 
b) Modify/create MCELL_HOME/etc/<cell>/mcell.trace to contain:
 ALL ALL stderr
 
c) Restart cell 

To stop the cell   

Make sure the cell process is completely stopped 
To start the cell 

mcell -n cellName

Note: This can also be done dynamically without the need to restart the cell:
 
mcfgtrace -n <cell> ALL ALL stderr
 
and to disable:
 
mcfgtrace -n <cell> ALL VERBOSE no
 
2.) To enable cell rule tracing:
 
a) Modify MCELL_HOME/etc/<cell>/mcell.conf to contain:
Trace=Yes
TraceRuleLevel=2
TraceFileSize=50M
 
b) Modify/create MCELL_HOME/etc/<cell>/mcell.trace to contain:
ALL ALL stderr
 
c) Restart cell
 
Note: This can also be done dynamically without the need to restart the cell (except the change to TraceFileSize):
 mcfgtrace -n <cell> ALL ALL stderr
mcontrol -n <cell> tracerule on
 
and to disable:
mcfgtrace -n <cell> ALL VERBOSE no
mcontrol -n <cell> tracerule off
 
3.) To enable very verbose cell rule tracing:
 
a) Modify MCELL_HOME/etc/<cell>/mcell.conf to contain:
Trace=Yes
TraceRuleLevel=2
TraceRulePorts=ALL
TraceFileSize=25M
 
b) Modify/create MCELL_HOME/etc/<cell>/mcell.trace to contain:
ALL ALL stderr
 
c) Restart cell
 
Note: This can also be done dynamically without the need to restart the cell (except the change to TraceFileSize):
mcfgtrace -n <cell> ALL ALL stderr
mcontrol -n <cell> tracerule on
mcontrol -n <cell> tracerule ports ALL
 
and to disable:
mcfgtrace -n <cell> ALL VERBOSE no
mcontrol -n <cell> tracerule off
mcontrol -n <cell> tracerule ports -ALL
 
 
4.) To enable cell rule tracing for phases:
mcontrol -n <cell> tracerule on
mcfgtrace -n <cell> ALL ALL stderr
mcontrol -n <cell> tracerule phases +refine                   (To enable for single phase)
mcontrol -n <cell> tracerule phases +refine, +new      (To enable multiple phases)
mcontrol -n <cell> tracerule phases +ALL                       (To enable for all phases)
 
To Disable Trace:
mcontrol -n <cell> tracerule off
mcfgtrace -n <cell> ALL VERBOSE no
mcontrol -n <cell> tracerule phases -refine                    (To disable for single phase)
mcontrol -n <cell> tracerule phases -refine, -new        (To disable for multiple phases)
mcontrol -n <cell> tracerule phases -ALL                        (To disable for all phases)
 
 
5.) To enable cell rule tracing for rules:
mcontrol -n <cell> tracerule on
mcfgtrace -n <cell> ALL ALL stderr
mcontrol -n <cell> tracerule names +ruleName                                 (To enable trace on a single rule)
mcontrol -n <cell> tracerule names +ruleName1, + ruleName2    (To enable trace for multiple rules)
mcontrol -n <cell> tracerule names +ALL:ALL                                    (To enable trace for all rules)
 
To disable trace:
mcontrol -n <cell> tracerule off
mcfgtrace -n <cell> ALL VERBOSE no
mcontrol -n <cell> tracerule names -ruleName                                   (To disable for single rule)
mcontrol -n <cell> tracerule names -ruleName1, -ruleName2       (To disable for multiple rules)
mcontrol -n <cell> tracerule names -ALL:ALL                                     (To disable for all rules)
 
Note: The logs will get stored at default location $MCELL_HOME\log\<cell>

Please remember to disable the trace level entries from the respective files after reproducing the issue or collecting logs after specific duration.

Demo for enabling cell rule level trace and increasing log file size: