This is probably a Mendix bug. However, it could also be the case that you're using an Oracle version that is not supported by Mendix.
Some databases automatically create an index for keys, and some don't. I'm guessing Mendix incorrectly assumes that Oracle does not, while in fact it does.
Your suggested workaround of manually executing the correct commands should work as a workaround (and this will not really result in any additional downtime, since you should prepare and test your ddl update script anyway).
Many thanks for your reply. In UAT we never faced this issue.It went fine.Only differnce is in UAT we had successive deployments one by one.In production we are directly doing the deployment of the latest mda file created with Modeller 5.21.5.
We have couple of UAT servers one in Mendix 4 and other one in Mendix 5. We have done functional changes in Mendix 4 and migration changes in Mendix 5 using different branch lines and then we finally Merged both the branches.
For example, we had deployed MDA file “100” in UAT A (Mendix4) and production(Mendix 4) . After that we have deployed mda 101, 102 till 105 in UAT server A (Mendix4) and then we merged the code and deployed mda 106 , 107 till 109 in UAT server B (Mendix 5).
Since this issue didn't occure in UAT server B, I followed the same approach in pre production environement. I delpoyed mda starting from 101 till 105 in Mendix 4 in pre production server, then I upgraded the Mendix console to 4.4 and mendix server to 5.21.5 and then deployed mda 106.
While deploying mda 106 it started to give issues in data syn up.
Not sure why it woked in UAT and why not in pre production environment. May be there are some restrictions on the database as you suggested.