I'm getting some of these prints in my console while running my application from Xcode 6 in my iPhone 6 with iOS 9 beta 5:
CoreData: Failed to load optimized model at path '/var/mobile/Containers/Bundle/Application/0000000B-BDBC-0000-000B-0000FB00000B/Distribution.app/database.momd/database.omo'
I've run into this issue and did some digging around.
I've been building with Xcode 6.4 and it looks like previously core data only produced a .mom file in the MyApp.ipa momd directory. This screenshot is from a project that has seen several version of Xcode.
Notice all the older model versions only have a .mom file. I just created a new model version today and it has both a .mom and an .omo file.
It appears that Xcode 6.4 (and perhaps some of the beta 7.x versions as well) do not know how to load the optimized version of the data model because I also get the
2015-10-16 11:11:42.563 MyAppName[1767:599635] CoreData: Failed to load optimized model at path '/var/mobile/Containers/Bundle/Application/D887D60B-FB28-4059-8167-F573460D98F8/MyAppName.app/MyDataModel.momd/MyDataModel3_0Analytics.omo'
warning when compiling with 6.4. However, when compiling the app with the latest app store version of Xcode (7.0.1) I do not get that warning. I'm guessing that the reason Mahesh's solution is working is because re-writing the entire schema creates the .omo file the app is looking for in the app bundle.
The solution for me was to generate a new data model version in core data and then build with Xcode 7. It seems that creating a new model version creates the optimized model file. In my testing though, even with this file created Xcode 6.4 still throws the error. It wasn't till I tried it with Xcode 7.0.1 that the warning went away.
This is speculation but I think if you have an existing project and have not created a new data model version and build with Xcode 7 that the .omo file is missing, so it's throwing the warning because it cannot find the file. However if you've versioned your data model and build with Xcode 6.4 it seems that the earlier Xcode version doesn't do something correctly with the optimized version and it doesn't load it even if its there. These are just my observations though.
I verified that I had an optimized model (.omo file) to load by doing the following: 1. archive your project 2. change the .ipa extension to .zip 3. expand your zip file 4. click on the "payload" folder and right click (or cmd click) on the app bundle in the folder and select "Show Package Contents". 5. click on the .momd directory, you should see all of your available managed object models there.
If all you have is .mom files and no .omo files then the warning makes complete sense, the app is unable to open a file that does not exist.
In my testing it seems like the warning was informational only. I never had any crashing because of it. It seems like core data may try to load the optimized model first, and if that fails fall back to the regular .momd model. This is merely my speculation though.
I'm not sure if everything here is entirely correct, this is just what I've observed so far in trying to debug this. If anyone else can contribute any more info I welcome your input.