On a Windows 7 PC, these files were getting enormous, and causing problems with the size of my roaming profile. Metalink Note ID 1943500.1 gives a solution for SQL Developer, which also seems to work for JDeveloper.

The all-resources.dat file can be found in:

C:\Users\UserName\AppData\Roaming\SQL Developer\system\system_cache\var\cache

and

C:\Users\UserName\AppData\Roaming\JDeveloper\system\system_cache\var\cache

The fix is as follows…

Add the following text to the sqldeveloper.conf file (in the sqldeveloper\bin directory):

AddVMOption -Dorg.netbeans.core.update.all.resources=never

For JDeveloper, add the same line of text to the jdev.conf file (in the jdev\bin directory).

The all-resources.dat files can then be permanently deleted (Shift-Delete) to free up a considerable amount of roaming profile space.