Open the folder that contains your catalog. Locate a file with the same name as your catalog but with the .lock extension. That lock file needs to be deleted, and then Lightroom will open again. Sometimes, when Lightroom doesn't shut down normally, this file can be left behind. Just delete that file and you will be able to get going again. It is the only file you should delete.
Thanks, I will try it.
when I opened the catalog folder is beyond the .lock, there appeared a .lrcat-journal.
that file is this?
Delete only the *.lock file. Delete nothing else.