Solution : https://service.sap.com/sap/support/notes/774339 (SAP Service marketplace login required)
Key words : 
prerequisites internal server error due, status internal server error, reasons solution due, internal server error, dtr server fail, server log files, design time repository, log viewer service, /tc~dtr~enterpriseapp, sap support line
Related Notes : 
       
| 1145663 | Initial Configuration of Usage Type DI: Common problems | 
| 1065492 | DuplicateKeyException on Central Server Startup in DTR | 
| 1051203 | system copy of DTR - checkin fails with NullPointerException | 
| 1001502 | OutOfMemory error during CMS import on Oracle 10g database | 
| 959218 | missing DTR database views after System Copy Tool migration | 
| 957190 | Socked closed errors when running DTR in cluster environment | 
| 955281 | CMS import fails due to an internal server error in DTR | 
| 955082 | Out of memory error during assembly in CMS | 
| 939041 | CMS Assembly fails on DB2 with Internal Server Error in DTR | 
| 876889 | Authorization problem in DTR when using LDAP user store | 
| 859465 | NullPointerException in DTR/XI | 
| 851602 | CMS Import/DTR Integrate fails on DB2 | 
| 828628 | CMS import fails with "Internal Server Error" | 
| 821939 | DTR import fails on Oracle 9.2.0.5 | 
| 784903 | Export and other DTR operations fail on DB2 with Status 500 | 
| 784340 | DTR Export fails with error "Internal Server error" | 
| 728788 | -602 AK Unexpected strategy information with join select | 
| 580612 | JDBC: Connection error when writing long strings |