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1.0
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October 24, 2018
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Maaz Khan
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About this Document
Background
This
document will cover use of ntp service to synchronize time with ntp servers.
Intended Audience
This
document is primarily meant for database administrators, system administrators,
Team Leaders, Technical Managers, etc.
References
https://docs.oracle.com/cd/E37670_01/E41138/html/section_m5p_j1h_pp.html
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/deployment_guide/s1-checking_the_status_of_ntp
https://www.ntppool.org/zone/om
https://www.howtogeek.com/tips/how-to-sync-your-linux-server-time-with-network-time-servers-ntp/
https://www.akadia.com/services/ntp_synchronize.html
Attachments
Table of Contents
Summary-
NTP stands for Network Time Protocol. NTP is
organized in a hierarchical client-server model. Top hierarchy contains
reference clocks. A reference clock also known as stratum 0 is cesium clock or
a Global Positioning System (GPS) that receives time from satellites.
Attached to these machines there are the
so-called stratum 1 servers (that is, stratum 0 clients), which are the top
level time servers available to the Internet, that is, they are the best NTP
servers available.
Following this hierarchy, the next level in
the structure are the stratum 2 servers which in turn are the clients for stratum
1 servers.
The lowest level of the hierarchy is made up
by stratum 16 servers.
Every server that is synchronized with a
stratum n server is termed as being at stratum n+1 level.
Choosing NTP Server for DCF –
As we do not have our own NTP server, we will
be using ntp server to check time on periodic basis over internet for on-prem servers which are ntp clients in this case –
pool.ntp.org project is a big virtual cluster
of timeservers providing reliable easy to use NTP service for millions of
clients. From list of servers across globe, this open source project has
suggested below ntp server list for Oman –
server 0.asia.pool.ntp.org
server 1.asia.pool.ntp.org
server 2.asia.pool.ntp.org
server 3.asia.pool.ntp.org
These servers are in Asia zone
Steps to configure ntp (tested in Clone)
Shutting down services-
1.
Shut down
apps services
adstpall apps/appspwd
Manually check and make sure if all application services are down.
ps -ef | grep applmgr
2. Shut down
database and listener
SQL> shut immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
3. Shut down
ASM
[oraprod@clone ~]$ source /home/oraprod/asm.env
[oraprod@clone ~]$ crsctl stop has
CRS-2791: Starting shutdown of Oracle High
Availability Services-managed resources on 'clone'
CRS-2673: Attempting to stop 'ora.CLONE.lsnr' on
'clone'
CRS-2673: Attempting to stop 'ora.DATA.dg' on 'clone'
CRS-2677: Stop of 'ora.CLONE.lsnr' on 'clone'
succeeded
CRS-2677: Stop of 'ora.DATA.dg' on 'clone' succeeded
CRS-2673: Attempting to stop 'ora.asm' on 'clone'
CRS-2677: Stop of 'ora.asm' on 'clone' succeeded
CRS-2673: Attempting to stop 'ora.evmd' on 'clone'
CRS-2677: Stop of 'ora.evmd' on 'clone' succeeded
CRS-2673: Attempting to stop 'ora.cssd' on 'clone'
CRS-2677: Stop of 'ora.cssd' on 'clone' succeeded
CRS-2793: Shutdown of Oracle High Availability
Services-managed resources on 'clone' has completed
CRS-4133: Oracle High Availability Services has been
stopped.
[oraprod@clone ~]$
NTP Configuration -
1. Update
NTP File –
vi /etc/ntp.conf
We will be using asia
ntp servers to synchronize them. This is because there are 0 servers assigned
for Oman and we did not find any server for UAE either.
Refer -
https://www.ntppool.org/zone/om
Backup file - /etc/ntp.conf
Comment below lines -
#server 0.rhel.pool.ntp.org
#server 1.rhel.pool.ntp.org
#server 2.rhel.pool.ntp.org
Add below lines -
#### new lines for Oman ntp servers
server 0.asia.pool.ntp.org
server 1.asia.pool.ntp.org
server 2.asia.pool.ntp.org
server 3.asia.pool.ntp.org
2. Start
ntpd service on Clone –
Service ntpd start
3. Stop ntpd
service to synchronize time
Service ntpd stop
4. Update
ntpd using ntpdate
/usr/sbin/ntpdate asia.pool.ntp.org
Synchronizing time every day using cron scheduler –
For security reasons, we have disabled internet to our server and hence
real time synchronization is not possible. In such case, we will be scheduling
synchronization after mid night 2 am using a script.
The script will –
1.
Enable internet by adding gateway
2.
Stop ntpd service
3.
Run ntpdate command
4.
Start ntpd service
5.
Disable internet by deleting gateway
Script Details –
[root@prod3
scripts]# cat ntp_sync.sh
#!/bin/bash
route add
default gw 195.1.1.8 eth0
service ntpd
stop
/usr/sbin/ntpdate
asia.pool.ntp.org
service ntpd
start
route
del default gw 195.1.1.8 eth0
exit
Post steps –
Startup services-
1.
Startup
asm
[oraprod@clone ~]$ crsctl start has
CRS-4123: Oracle High Availability Services has been
started.
[oraprod@clone ~]$ crsctl stat res -t
----------------------------------------------------------------------------
Name
Target State Server State details
----------------------------------------------------------------------------
Local Resources
----------------------------------------------------------------------------
ora.CLONE.lsnr
ONLINE OFFLINE clone STABLE
ora.DATA.dg
ONLINE ONLINE clone STABLE
ora.asm
ONLINE ONLINE
clone
Started,STABLE
ora.ons
OFFLINE OFFLINE clone STABLE
----------------------------------------------------------------------------
Cluster Resources
----------------------------------------------------------------------------
ora.clone.db
1 OFFLINE OFFLINE Instance
Shutdown,ST
ABLE
ora.cssd
1 ONLINE
ONLINE clone STABLE
ora.diskmon
1 OFFLINE OFFLINE STABLE
ora.evmd
1 ONLINE
ONLINE clone STABLE
----------------------------------------------------------------------------
Manually check and make sure if all application services are down.
ps -ef | grep applmgr
2. Start database
and listener
SQL> startup
ORA-32004: obsolete or deprecated parameter(s)
specified for RDBMS instance
ORACLE instance started.
Total System Global Area 2.1475E+10 bytes
Fixed Size 3722144 bytes
Variable Size 1543504992 bytes
Database Buffers 1.9864E+10 bytes
Redo Buffers 63385600 bytes
Database mounted.
Database opened.
[oraprod@clone ~]$ lsnrctl start CLONE
3. Start
apps node
[applprod@clone ~]$ adstrtal.sh apps/appspwd
Validation-
1. Logon to
Oracle Applications and validate –
2. Logon to Backend
server and validate –
Issue faced -
[root@clone
~]# /usr/sbin/ntpdate pool.ntp.org
24 Oct
10:26:16 ntpdate[730]: no server suitable for synchronization found
Solution
-
Make sure
server is accessible to internet.
