The internal time of Oracle sysdate is inconsistent with that of the Operating System

Oracle 11g RAC, internal time is synchronized through the ctss service, during installation, ntpd will be removed by default, using ctss.
However, after running for a period of time, it is found that there is a time difference between the oracle internal time and the operating system. Therefore, the oracle database and the operating system need a time synchronization server;

/Sbin/service ntpd status
Ntpd (pid 4403) is running...

Ps-ef | grep ntp
Ntp 2113 1 0 Dec09? At 00:00:00 ntpd-u ntp: ntp-p/var/run/ntpd. pid-x

Grep OPTIONS/etc/sysconfig/ntpd
OPTIONS = "-u ntp: ntp-p/var/run/ntpd. pid-x"

To start:

/Sbin/service ntpd start

[Grid @ rac01 ~] $ Crsctl check ctss
The CRS-4701: The Cluster Time Synchronization Service is in Active mode.
CRS-4702: Offset (in msec): 0
 
When the ctss detects that there is ntp on the system, it automatically switches the mode to the passive mode.
[Grid @ HBCADB001 ~] $ Crsctl check ctss
The CRS-4700: The Cluster Time Synchronization Service is in Observer mode.
 
SQL> select sessiontimezone, to_char (sysdate, 'yyyymmdd hh24: mi: ss') from dual;
SESSIONTIMEZONE
---------------------------------------------------------------------------
TO_CHAR (SYSDATE ,'
-----------------
+ 08:00
14:14:10 20121029

SQL>! Date
Mon Oct 29 14:14:13 CST 2012
SQL>