Migration processing is substantially improved in Inventor 2008. This white paper describes the improvement and how it affects your adoption of Inventor 2008.
Migration In Earlier Inventor Versions
Migration behavior in Autodesk Inventor 2009 is unchanged from Autodesk Inventor 2008. The following information describes Inventor 2008 behavior, and is also appropriate to Inventor 2009. Because Migration is a complicated process, it is easiest to explain the improvements in Inventor 2008 by describing how things worked in earlier Inventor releases.
Migration is the processing Inventor does when it opens a file last saved by an earlier version of Inventor. More exactly, migration is the extra processing over and above the normal open processing. Prior to Inventor 2008, migration was expensive in both performance and capacity terms. Opening an assembly consisting entirely of Inventor 10 files in Inventor 11 took longer and consumed more memory than opening that same assembly once it was saved in version 11 format. Typical migration costs varied from file to file, but would generally double the time of opening a file.
If you open a file last saved by an earlier version of Inventor, migration always takes place. When adopting a new release of Inventor, you have a choice whether to perform implicit or explicit migration.
In implicit migration, you work with your old files normally without running through any special process. The files remain in the old form until you decide to change them (for example, you change the design information). As you change these files and save them back to disk, they are stored in the latest Inventor format and migration is no longer necessary when they are re-opened.
In explicit migration, the enterprise goes through a special process where the old data is resaved using the new version of Inventor. This explicit migration is generally done by the CAD Manager prior to making the new version of Inventor available to all the engineers. Autodesk provides the Task Scheduler to help automate explicit migration.
Prior to Inventor 2008, the migration cost was so high during opening a file that implicit migration was not very attractive and Inventor users with substantial amounts of data used to take the explicit migration route. It was more efficient to run through the ”one-time” cost of explicit migration than to continually pay the migration cost on opening old files. Although the Task Scheduler helped in the process, explicit migration made adoption of a new Inventor release expensive because all the files had to be migrated before engineers could start working with them.
Once files are saved using a new version of Inventor, they cannot be read by an earlier version of Inventor. This means that once explicit migration happens, everyone working with these files must use the new version of Inventor. Explicit migration tends to force an enterprise to adopt a very controlled, synchronized roll-out of a new release.
Migration in Inventor 2008
Migration in Inventor 2008 is no longer an expensive process provided the files are saved in version 11 (or later) form. In the tests Autodesk did with such files, the migration cost is generally negligible. Typical migration cost is generally less than 10% of the time of a non-migrating open, though this cost can vary from file to file.
If the files are saved in version 10 (or earlier) form, migration remains an expensive process.
For users adopting Inventor 2008, we recommend you do not perform explicit migration if the files are in version 11 (or later) form. Work normally and let migration happen implicitly. You can still perform explicit migration if you really want to, although there is no compelling need to do so. If you want to perform explicit migration, it’s best to use the Task Scheduler, but you can also use the new File > Migrate command inside Inventor.
For files saved in version 10 (or earlier) form, the decision to migrate explicitly or implicitly is essentially the same in Inventor 2008 as in earlier releases. Small amounts of data are probably better migrated implicitly, but if you frequently open large designs saved in version 10 (or earlier) form it is probably better to perform explicit migration using the Task Scheduler.
Because explicit migration is not necessary, it is easier for an enterprise to adopt a new release more flexibly.
Determining the Version of Inventor That Last Saved a File
To decide whether to explicitly or implicitly migrate your data, you must know the version of Inventor last used to save that file.
The easiest way to determine this is to open the Design Assistant (click Start > All Programs > Autodesk > Autodesk Inventor 2008 > Design Assistant 2008), and then open the design file. You may have to use File > Projects before using File >Open. The appropriate property is called “Last Update With” (this actually means “Last Saved Using”) and can use View > Customize and View >Details before seeing the value of this field in Design Assistant.
In a large assembly, some files may have been saved using different versions of Inventor.
Application Options and Migration
An Application Option (Save options, Prompt to save for migration) can be checked. When you close a file that migrated on open, it asks if you want to save it. If set, this tends to encourage you to save files that migrated on open, even though you haven’t logically changed them (for example, you made no design change).
By default, this option is off and we recommend that you leave it off.
Note: This Application Option is not used if you perform explicit migration using the Task Scheduler or through the File > Migrate command.
(The behavior of this application option is unchanged in Inventor 2008).
As stated previously, once a file is saved using a particular version of Inventor (for example, Inventor 2008), that file cannot be read by an earlier version of Inventor (for example, Inventor 11). Be careful when saving a file that underwent migration (Inventor always warns you when you do a save). You can also ensure a file is not saved in this state accidentally by write-protecting the file.
(This save behavior is unchanged in Inventor 2008).