PRVF-5439 : NTP daemon does not have slewing option "-x"

       客户环境是Oracle 11.2.0.3 RAC Database for IBM AIX，在其中一个Clusterware日志中有如下告警信息：

PRVF-5436 : The NTP daemon running on one or more nodes lacks the slewing option "-x"

PRVF-5439 : NTP daemon does not have slewing option "-x" set on node "afab2"

PRVF-5439 : NTP daemon does not have slewing option "-x" set on node "afab1"

        针对这个问题，在METALINK文章《保持 RAC 群集环境稳定当前必须要做的 11 件事 [ID 1525819.1]》文章中有如下描述：

11. 使用 slewing 选项实施 NTP

适用平台：  所有 Linux 和 Unix 平台。

原因： 如果没有 slewing 选项，在时间差异超过特定（取决于平台）阈值时，NTP 将向前或向后调整系统时钟。大幅度向后调整时间会导致 Clusterware 以为错过了签到，从而发生节点驱逐的情况。出于此原因，我们强烈建议将 NTP 配置调整为 slewing time （加快或减慢）时钟时间以同步时间，以防止此类驱逐情况的发生。有关如何在您的平台上实施 NTP 时间调整的更多信息，请参考平台特定的 RAC 与 Oracle Clusterware 最佳实践和初学者指南文档（见下文）。

        在官方手册中对该问题也做了详细的描述：

AIX平台：

2.11 Network Time Protocol Setting

Oracle Clusterware requires the same time zone setting on all cluster nodes. During installation, the installation process picks up the time zone setting of the Grid installation owner on the node where OUI runs, and uses that on all nodes as the default TZ setting for all processes managed by Oracle Clusterware. This default is used for databases, Oracle ASM, and any other managed processes.

You have two options for time synchronization: an operating system configured network time protocol (NTP), or Oracle Cluster Time Synchronization Service. Oracle Cluster Time Synchronization Service is designed for organizations whose cluster servers are unable to access NTP services. If you use NTP, then the Oracle Cluster Time Synchronization daemon (ctssd) starts up in observer mode. If you do not have NTP daemons, then ctssd starts up in active mode and synchronizes time among cluster members without contacting an external time server.

Note:

Before starting the installation of Oracle Grid Infrastructure, Oracle recommends that you ensure the clocks on all nodes are set to the same time.

If you have NTP daemons on your server but you cannot configure them to synchronize time with a time server, and you want to use Cluster Time Synchronization Service to provide synchronization service in the cluster, then deactivate and deinstall the NTP.

To disable the NTP service, run the following command as the root user

# stopsrc -s xntpd

When the installer finds that the NTP protocol is not active, the Cluster Time Synchronization Service is installed in active mode and synchronizes the time across the nodes. If NTP is found configured, then the Cluster Time Synchronization Service is started in observer mode, and no active time synchronization is performed by Oracle Clusterware within the cluster.

To confirm that ctssd is active after installation, enter the following command as the Grid installation owner:

$ crsctl stat resource ora.ctssd -t -init

If you are using NTP, and you prefer to continue using it instead of Cluster Time Synchronization Service, then you need to modify the NTP initialization file to enable slewing, which prevents time from being adjusted backward. Restart the network time protocol daemon after you complete this task.

To do this on AIX, configure the XNTP daemon to start at each system restart by editing the file /etc/rc.tcpip:

1. Open the /etc/rc.tcpip file, and locate the following line:

   start /usr/sbin/xntpd "$src_running"

2. Change the line to the following:

   start /usr/sbin/xntpd "$src_running" "-x"

3. Save the file.

To enable XNTP after it has been disabled, enter the following command on each cluster member node:

# startsrc -s xntpd -a "-x"

        参考文章：《Oracle® Grid Infrastructure Installation Guide

11g Release 2 (11.2) for IBM AIX on POWER Systems (64-Bit)

E24614-03》http://docs.oracle.com/cd/E11882_01/install.112/e24614/preaix.htm#CEGBDEJJ


Linux平台：

2.11 Network Time Protocol Setting

Oracle Clusterware requires the same time zone setting on all cluster nodes. During installation, the installation process picks up the time zone setting of the Grid installation owner on the node where OUI runs, and uses that on all nodes as the default TZ setting for all processes managed by Oracle Clusterware. This default is used for databases, Oracle ASM, and any other managed processes.

You have two options for time synchronization: an operating system configured network time protocol (NTP), or Oracle Cluster Time Synchronization Service. Oracle Cluster Time Synchronization Service is designed for organizations whose cluster servers are unable to access NTP services. If you use NTP, then the Oracle Cluster Time Synchronization daemon (ctssd) starts up in observer mode. If you do not have NTP daemons, then ctssd starts up in active mode and synchronizes time among cluster members without contacting an external time server.

Note:

Before starting the installation of Oracle Grid Infrastructure, Oracle recommends that you ensure the clocks on all nodes are set to the same time.

If you have NTP daemons on your server but you cannot configure them to synchronize time with a time server, and you want to use Cluster Time Synchronization Service to provide synchronization service in the cluster, then deactivate and deinstall the NTP.

To deactivate the NTP service, you must stop the existing ntpd service, disable it from the initialization sequences and remove the ntp.conf file. To complete these step on Oracle Linux, and Asianux systems, run the following commands as the root user

# /sbin/service ntpd stop# chkconfig ntpd off# rm /etc/ntp.conf

or, mv /etc/ntp.conf to /etc/ntp.conf.org.

Also remove the following file:

/var/run/ntpd.pid

This file maintains the pid for the NTP daemon.

When the installer finds that the NTP protocol is not active, the Cluster Time Synchronization Service is installed in active mode and synchronizes the time across the nodes. If NTP is found configured, then the Cluster Time Synchronization Service is started in observer mode, and no active time synchronization is performed by Oracle Clusterware within the cluster.

To confirm that ctssd is active after installation, enter the following command as the Grid installation owner:

$ crsctl check ctss

If you are using NTP, and you prefer to continue using it instead of Cluster Time Synchronization Service, then you need to modify the NTP configuration to set the -x flag, which prevents time from being adjusted backward. Restart the network time protocol daemon after you complete this task.

To do this, on Oracle Linux, Red Hat Linux, and Asianux systems, edit the /etc/sysconfig/ntpd file to add the -x flag, as in the following example:

# Drop root to id 'ntp:ntp' by default.PTIONS="-x -u ntp:ntp -p /var/run/ntpd.pid"# Set to 'yes' to sync hw clock after successful ntpdateSYNC_HWCLOCK=no# Additional options for ntpdateNTPDATE_OPTIONS=""

Then, restart the NTP service.

# /sbin/service ntp restart

On SUSE systems, modify the configuration file /etc/sysconfig/ntp with the following settings:

NTPD_OPTIONS="-x -u ntp"

Restart the daemon using the following command:

# service ntp restart

        参考文章：《

Oracle® Grid Infrastructure Installation Guide
11g Release 2 (11.2) for Linux

》http://docs.oracle.com/cd/E11882_01/install.112/e10812/prelinux.htm#BABECGII

请在实施的时候注意该问题！