ORACLE restarted

Hi all,

My DB restarted on 27,Mar, 2017, I have search for sometimes,but can not find out the root cause.

Please give me some advice on this issues.

Below are the log I saw in log.xmp

<msg time='2017-03-27T21:01:00.362+07:00' org_id='oracle' comp_id='rdbms'

msg_id='opiabt1:2549:2031367711' type='NOTIFICATION' group='shutdown'

level='16' host_id='dbra' host_addr='10.149.249.8'

pid='9571'>

<txt>License high water mark = 355

</txt>

</msg>

<msg time='2017-03-27T21:01:03.831+07:00' org_id='oracle' comp_id='rdbms'

type='UNKNOWN' level='16' host_id='dbra'

host_addr='10.149.249.8' module='JDBC Thin Client' pid='8644'>