Today while restarting my WLS_FORMS server, I came across a error “The file store “WLS_DIAGNOSTICS” could not be opened because it contained a file with the invalid version 1. A file of version 2 was expected.”

Part of Error Log was as follows:
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There are 1 nested errors:

weblogic.store.PersistentStoreException: [Store:280073]The file store “WLS_DIAGNOSTICS” could not be opened because it contained a file with the invalid version 1. A file of version 2 was expected.
at weblogic.store.io.file.FileStoreIO.open(FileStoreIO.java:107)
at weblogic.store.internal.PersistentStoreImpl.recoverStoreConnections(PersistentStoreImpl.java:413)
at weblogic.store.internal.PersistentStoreImpl.open(PersistentStoreImpl.java:404)
at weblogic.store.xa.PersistentStoreManagerXA.createFileStore(PersistentStoreManagerXA.java:120)
at weblogic.diagnostics.archive.DiagnosticStoreRepository.getStore(DiagnosticStoreRepository.java:91)
at weblogic.diagnostics.lifecycle.DiagnosticSystemService.start(DiagnosticSystemService.java:128)
at weblogic.t3.srvr.SubsystemRequest.run(SubsystemRequest.java:64)
at weblogic.work.ExecuteThread.execute(ExecuteThread.java:201)
at weblogic.work.ExecuteThread.run(ExecuteThread.java:173)

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After lot of searching and headbanging I came across following thread http://forums.oracle.com/forums/thread.jspa?threadID=684783

I followed the advice of the user “user2696444” and did as follows:

Step 1. Shutdown Servers (including Weblogic Admin Server plus opmn components)

Step 2. Under DOMAIN HOME (in my case it was D:\oracle\Middleware\user_projects\domains\ClassicDomain) I search for *.DAT and deleted those files with capital letters .DAT and not small letters .dat

Step 3. Under DOMAIN HOME then I search for *.lok and deleted all the files that I found.

Step 4. Then Started Admin Server plus all the other servers including opmn components.

that it, after that I could see my WLS_FORMS in green and up