It's quite normal to upgrade the runtime (executables) to newer versions while leaving the database (application) as it is. This will enable the new runtime features such as Web Services. Recently we have seen a number of questions about whether you can upgrade older databases to NAV 2009. As such, NAV 2009 is just another version, so the default answer would be that yes, you can do that.
Just remember a few additional things to be avare of:
1) There is one potential issue: NAV 2009 has a change from older versions that comparing characters in a CASE structure is case sensitive. For example:
CodeVar := 'A';
CASE CodeVar OF
In version 5 you will get the message. In NAV 2009 you won't. This has one specific implication in the standard application. Most matrix forms have a function called "DimCodeToOption". As an example is Form 113 Budget. The function has a parameter "DimCode" which in version 5 was type Code. This has to be changed to Text. Otherwise, the case sensitive comparison will fail, and Matrix forms will not show any data. So make this change in Form 113 and other forms, for example Form 554 "Analysis by Dimensions". And if you find other matrix forms have stopped working, then check this first.
2) If you want to run RTC, then of course you would also have to import pages or run transformation first.
3) Once you upgrade objects to NAV2009 runtime, you cannot use the objects in previous versions again, even if you export them and import into for example a NAV 5 database. NAV2009 adds new properties to objects which older versions will not be able to handle.
A number of customers have already made the change to NAV 2009 runtime, and to my knowledge no other issues have been reported regarding running the older database in a newer runtime. If you do find any issues not mentioned here, then please do add a comment below,
These postings are provided "AS IS" with no warranties and confer no rights. You assume all risk for your use.
Lars Lohndorf-Larsen (Lohndorf)
Microsoft Dynamics UK
Microsoft Customer Service and Support (CSS) EMEA