I apoligize for the much delayed response and hope that you were able to get your questioned answered through another method such as CDN Customer Support or your local AE.
For the benefit of the forum and other users I'll provide a response.
In response to your first question, "Does anyone know where i can get a detailed report on unsuccessful/incomplete routes in VCAR i.e why did it not complete?" Yes, their are several reports that you can generate to get information in VCAR. For your specific request you can try the following report:
Other reports that you can use:
Report > Net
In response to your observation related to your first question, "I can see that some of the unrouted nets would be easily done by hand." there are several ways to analyse and investigate why a connection is not made. First, if the connection failed automatically try to route it interactively. If it succeeds it may indicate an autorouter setup problem or bug. If it cannot route interactively or automatically it may indicate that the connection point is blocked or a rule is set prohibiting the connection. Make sure to also use the 'check' and 'report' features to show conflicts which may indicate the cause of the incomplete net.
In response to your second question, "Does VCAR get its connectivity from the layout / schematic / somewhere else?" it really depends on your design flow and tools. VCAR can get it's connectivity from a variety of sources including the connectivity associated with the design in VXL from the layout and schematic in CDB and OA formats, DEF, translation from proprietary applications that generate the correctly formatted netlist section in the design file.
I suggest referencing the Virtuoso Chip Assembly Router Guide if using a Virtuoso flow.
For IC5141 CDB reference: http://sourcelink.cadence.com/docs/files/Release_Info/Docs/iccausr/iccausr5.2.51/iccausrTOC.html
For IC61x OA reference: http://sourcelink.cadence.com/docs/files/Release_Info/Docs/iccausr/iccausr6.1.3/iccausrTOC.html
I hope this answers your questions. If not, feel free to add to the post. I also recommend contacting Customer Support and your local AE to assist you in your use of VCAR.
Sr. Technical Leader
Technical Field Operations, North America-Central Region