SAP Message 753479
Questions from SAP are in Bold my answers are in regular font.
To me the history of DC cmc.com/java/ext_lib in compartment
SAP_ESS in the track ZXSS12MD.
According this the vendor cmc.com this DC is not from SAP.
This is a custom DC in the ZXSS12MD track. (Just contains one jar file).
When was this DC created? Has it been deleted in the meantime?
According to DTR this DC was created on 08/14/2009.
Here is the screen shot of the DTR Version History screen.

This DC has not been deleted.
The syncdb entry you have sent points to the following location in DTR:
http://am270s6409:52600/dtr/ws/ZXSS12MD/sap.com_SAP_ESS/dev/inactive/DCs/cmc.com/java/ext_lib/_comp/
Could you please check in the DTR Web UI which files are located
underneath this folder?
This is a screen shot of what is underneath the _comp folder of the DC in DTR.
In addition check in the DTR folder
http://am270s6409:52600/dtr/ws/ZXSS12MD/sap.com_SAP_ESS/dev/inactive/SCs/sap.com/SAP_ESS/_comp/TopLevelDCs
if there is a .dcref file that has the string ext_lib in its name.
Yes there is a dcref file with the name ext_lib in it. (The file itself is empty).
Does the DC java/ext_lib appear in the SAP_ESS compartment of CBS build
space ZXSS12MD_dev ?
Yes. Screen shot attached.
Are any files located underneath the folder
C:\santy\wd_dtc\0\DCs\cmc.com\java\ext_jars\_comp
that is mentioned in the error message?
I have attached a zip file of what is contained in the folder (starting from cmc.com folder)