The following are the most common reasons:
A system crash
The /var directory is running out of space
A corrupted wtmpx file
If the active.MMDD file exists, check it first for error messages. If the active and lock files exist, check the fd2log file for any relevant messages.
Run without arguments, the runacct script assumes that this invocation is the first invocation of the day. The argument MMDD is necessary if the runacct script is being restarted and specifies the month and day for which the runacct script reruns the accounting. The entry point for processing is based on the contents of the statefile file. To override the statefile file, include the desired state on the command line. For a description of the available states, see the runacct(1M) man page.
When you run the runacct program manually, be sure to run it as user adm.