weblogic.management.provider.EditSaveChangesFailedException

I try to activate a session in WLS, and I get this
java.lang.RuntimeException: weblogic.management.provider.EditSaveChangesFailedException
caused by

java.io.IOException: No such file or directory at java.io.UnixFileSystem.createFileExclusively(Native Method) at java.io.File.createNewFile(File.java:883) at weblogic.management.provider.internal.DescriptorHelper.getRecoveryFileForNewFile(DescriptorHelper.java:205) at weblogic.management.provider.internal.DescriptorHelper.saveDescriptorTree(DescriptorHelper.java:122) at weblogic.management.provider.internal.DescriptorHelper.saveDescriptorTree(DescriptorHelper.java:49) at weblogic.management.provider.internal.EditAccessImpl.saveChanges(EditAccessImpl.java:704) ... 133 more

It turned out that the file system was full :o(

No disk space monitoring? Ahi Ahi Ahi....