Do you know if I can execute the DDSDCLM that comes with R12 to check the Datacom R11 Data Dictionary using -SDC 120,PROD?
Before upgrading to 12.0 you use DDSDCLM with SDC 114,PROD to check if your DataDictionary 11.0 is valid and ready to be upgraded.
Before upgrading to 14.0 you use DDSDCLM with SDC 120,PROD to check if your DataDictionary 12.0 is valid and ready to be upgraded.
The DataDictionary basis modules for comparison are not the same in 11.0 and 12.0. They are different for each release.
So, executing DDSDCLM with SDC 120,PROD against a DataDictionary r11 environment will not be helpful.
You will get discrepancies not necessarily easy to explain.
I would not recommend to do that.