I have moved your discussion here for your convenience because it was posted on the Japanese community. I believe that this community is more suitable for your question.
Please search for McAfee support article: KB76720 - How to identify why the ePO database is very large.
This will help you identify the cause.
You should note however that ePO 4.5 is no longer suppported, it reached end of life Dec 31st 2013.
Once you have resolved this an upgrade is strongly recommended.
Check out the following blog posts to set up DB maintenance: