DS 86 was never tested on 4.x and is not supported. You can try it, but if you run into problems that you, nor the forum, nor any other tech forum can figure out, then TS. Novell won't support. You will get told to upgrade the NOS.
You do not have the option of merging the tree's, your enviroment does not fit the requirements. To do a merge both soruce and destination server MUST be running the same DS and have identical schema's.
Get your customer off of ccMail: And test those DOS apps.
If your test bed works fine, then go with the migration accross the wire (see this forums FAQ for help on that).
If your client is not giving you the time to do a test, be sure to explain to them very clearly and very slowly why you need to do this. If all else fails, here is what I tell my customers. I can build a test bed, and the time will be billable. I will use this test bed to ensure the migration will work with out issues. OR I can just jump forward and get it done THEN we wait and see what hand we got in this poker game. You MIGHT get everything working fine, but you are dealing with out dated software that has questions on compatibility (and no manufacture support). More than likely you WILL run into issues and it will affect the bottom line.
In my 6 years of doing consulting work, I have found that I can bill out more hours when the customer does not want me to do a test bed (the choice is normaly made because some CxO wants it done NOW and doesn't understand all the veriables). It may be great and wonderfull that I get to bill out more hours when I'm not allowed to do planning and testing, but it affects the customer relationship and can put both parties in a bad light. When I do the planning and I do the testing, my installs go smooth with little to no issues (most already found in test bed and resolution ready to implement if needed).
Give your customer the options and let them roll the dice.
Remember, testing is billable time and there is no such thing as a warranty on software functionality. Many customers try to dispute the hours for testing and resolving issues after a migration (they seem to think it should be free). Some customers I have run into seem to think that if I'm a CNE than I can just jump in and get it done. They don't understand that each network is completly different in design and veriables. A good way to work around this one is to get the customer to pay you up front. IF you have this type of contract, do not under estimate, always over estimate. It makes you look good when you finnsih before the estimate and it also ensures you get paid for all of the hours you put in.
Brent Schmidt CNE, Network +
Senior Network Engineer
KIS Computer Center