Cluster Time Synchronization Service(CTSS)可以檢測(cè)集群中節(jié)點(diǎn)之間的時(shí)間同步問題。CTSS被作為Oracle CLusterware的一部分進(jìn)行安裝。如果它檢測(cè)到在系統(tǒng)中存在時(shí)間同步服務(wù)(比如NTP或Chrony)或者存在時(shí)間同步服務(wù)配置是valid或broken，那么它將以觀察模式運(yùn)行。例如，如果集群中的任何一個(gè)節(jié)點(diǎn)上 存在/etc/ntp.conf文件，那么就算沒有運(yùn)行時(shí)間同步服務(wù)CTSS也會(huì)以觀察模式運(yùn)行。如果CTSS在集群的任何一個(gè)節(jié)點(diǎn)上都沒有檢測(cè)到存在時(shí)間同步服務(wù)或時(shí)間同步服務(wù)配置信息，它就會(huì)變成主動(dòng)模式運(yùn)行并且對(duì)集群執(zhí)行時(shí)間管理。如果CTSS在集群中的一個(gè)節(jié)點(diǎn)上以主動(dòng)模式運(yùn)行，在另一個(gè)節(jié)點(diǎn)上以觀察模式運(yùn)行，并且沒有NTP，時(shí)間同步軟件在運(yùn)行，那么你可以通過創(chuàng)建一個(gè)名叫/etc/ntp.conf的文件來將CTSS修改為觀察模式。對(duì)于CTSS改變?yōu)橛^察模式 會(huì)在alert.log中寫入消息。當(dāng)節(jié)點(diǎn)加入集群時(shí)，如果CTSS以主動(dòng)模式運(yùn)行時(shí)，那么它將會(huì)使用集群中存在引用時(shí)鐘的節(jié)點(diǎn)與這些加入節(jié)點(diǎn)進(jìn)行時(shí)間比較。如果兩個(gè)時(shí)間之間存在差異并且這種差異在特定設(shè)置限制，那么CTSS將執(zhí)行時(shí)間同步。集群中的時(shí)鐘節(jié)點(diǎn)由于各種原因?qū)⒉荒苁褂靡脮r(shí)鐘(CTSS用來作為基礎(chǔ)的時(shí)間,它所在的節(jié)點(diǎn)是集群中第一個(gè)啟動(dòng)的節(jié)點(diǎn))進(jìn)行同步。當(dāng)發(fā)生這種情況時(shí)，CTSS執(zhí)行回轉(zhuǎn)時(shí)間同步，它將加速或減慢節(jié)點(diǎn)上的系統(tǒng)時(shí)間直到它們與引 用系統(tǒng)時(shí)間處于同步狀態(tài)。在這種時(shí)間同步方法中，CTSS不會(huì)向后調(diào)整時(shí)間，它將保證系統(tǒng)時(shí)間單向增加。

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當(dāng)Orale集群軟件啟動(dòng)時(shí)，如果CTSS以主動(dòng)模式運(yùn)行并且時(shí)間差異超過了設(shè)置限制(限制為24小時(shí))，那么CTSS會(huì)在alert.log中生成一個(gè)告警，并退出，那么Oracle集群軟件會(huì)啟動(dòng)失敗。如果你必須手動(dòng)對(duì)加入集群的節(jié)點(diǎn)進(jìn)行時(shí) 間調(diào)整，在啟動(dòng)Oracle集群軟件之后CTSS可以對(duì)這些節(jié)點(diǎn)管理時(shí)間。當(dāng)執(zhí)行回轉(zhuǎn)時(shí)間同步時(shí)，CTSS從來不會(huì)使用引用時(shí)鐘向后調(diào)整時(shí)間。CTSS定期寫包含它如何使用引用時(shí)鐘來調(diào)整節(jié)點(diǎn)時(shí)間的告警到alert.log中。

CTSS當(dāng)出現(xiàn)以下情況下會(huì)向Oracle集群alert.log與syslog中寫告警信息:
.檢查到時(shí)間發(fā)生改變
.檢查到與引用時(shí)鐘相比存在著顯著的時(shí)間差異
.從觀察模式切換到主動(dòng)模式或者從主動(dòng)模式切換到觀察模式

使用CTSS來同步集群中的時(shí)間可以促進(jìn)對(duì)Oracle集群?jiǎn)栴}的診斷，因?yàn)椴恍枰紤]不同節(jié)點(diǎn)上影響時(shí)間的一系列事件了。
激活與禁止集群時(shí)間同步
為了對(duì)集群設(shè)置定時(shí)間管理服務(wù)可以激活CTSS。如果想要使用不同的集群時(shí)間同步服務(wù)可以禁止CTSS。為了激活CTSS，必須要對(duì)集群中的所有節(jié)點(diǎn)停止與刪除第三方的時(shí)間同步服務(wù)。當(dāng)激活CTSS時(shí)會(huì)檢查集群的時(shí)間管理服務(wù)方式。
下面的RAC因?yàn)樗泄?jié)點(diǎn)存在第三方的時(shí)間同步服務(wù)配置信息使得CTSS以觀察方式運(yùn)行
檢測(cè)集群節(jié)點(diǎn)是否存在第三方時(shí)間同步服務(wù)

[root@jytest1 ~]# find / -name ntp.conf
/etc/ntp.conf


[root@jytest2 ~]# find / -name ntp.conf
/etc/ntp.conf


[grid@jytest1 ~]$ cluvfy comp clocksync -n all

Verifying Clock Synchronization ...
CTSS is in Observer state. Switching over to clock synchronization checks using NTP

  Verifying Network Time Protocol (NTP) ...
    Verifying '/etc/ntp.conf' ...PASSED
    Verifying '/etc/chrony.conf' ...PASSED
    Verifying '/var/run/chronyd.pid' ...PASSED
    Verifying Daemon 'chronyd' ...PASSED
    Verifying NTP daemon or service using UDP port 123 ...PASSED
    Verifying chrony daemon is synchronized with at least one external time source ...FAILED (PRVG-13606)
  Verifying Network Time Protocol (NTP) ...FAILED (PRVG-1063)
Verifying Clock Synchronization ...FAILED (PRVG-1063, PRVG-13606)

Verification of Clock Synchronization across the cluster nodes was unsuccessful on all the specified nodes.


Failures were encountered during execution of CVU verification request "Clock Synchronization across the cluster nodes".

Verifying Clock Synchronization ...FAILED
  Verifying Network Time Protocol (NTP) ...FAILED
  PRVG-1063 : configuration files for more than one time synchronization
  service were found on nodes of the cluster
  configuration file "/etc/chrony.conf" was found on nodes "jytest2,jytest1"
  configuration file "/etc/ntp.conf" was found on nodes "jytest2,jytest1"

    Verifying chrony daemon is synchronized with at least one external time
    source ...FAILED
    jytest2: PRVG-13606 : chrony daemon is not synchronized with any external
             time source on node "jytest2".

    jytest1: PRVG-13606 : chrony daemon is not synchronized with any external
             time source on node "jytest1".


CVU operation performed:      Clock Synchronization across the cluster nodes
Date:                         Mar 3, 2018 12:58:07 AM
CVU home:                     /u01/app/product/12.2.0/crs/
User:                         grid

[grid@jytest2 ~]$ cluvfy comp clocksync -n all

Verifying Clock Synchronization ...
CTSS is in Observer state. Switching over to clock synchronization checks using NTP

  Verifying Network Time Protocol (NTP) ...
    Verifying '/etc/ntp.conf' ...PASSED
    Verifying '/etc/chrony.conf' ...PASSED
    Verifying '/var/run/chronyd.pid' ...PASSED
    Verifying Daemon 'chronyd' ...PASSED
    Verifying NTP daemon or service using UDP port 123 ...PASSED
    Verifying chrony daemon is synchronized with at least one external time source ...FAILED (PRVG-13606)
  Verifying Network Time Protocol (NTP) ...FAILED (PRVG-1063)
Verifying Clock Synchronization ...FAILED (PRVG-1063, PRVG-13606)

Verification of Clock Synchronization across the cluster nodes was unsuccessful on all the specified nodes.


Failures were encountered during execution of CVU verification request "Clock Synchronization across the cluster nodes".

Verifying Clock Synchronization ...FAILED
  Verifying Network Time Protocol (NTP) ...FAILED
  PRVG-1063 : configuration files for more than one time synchronization
  service were found on nodes of the cluster
  configuration file "/etc/chrony.conf" was found on nodes "jytest2,jytest1"
  configuration file "/etc/ntp.conf" was found on nodes "jytest2,jytest1"

    Verifying chrony daemon is synchronized with at least one external time
    source ...FAILED
    jytest2: PRVG-13606 : chrony daemon is not synchronized with any external
             time source on node "jytest2".

    jytest1: PRVG-13606 : chrony daemon is not synchronized with any external
             time source on node "jytest1".


CVU operation performed:      Clock Synchronization across the cluster nodes
Date:                         Mar 3, 2018 1:11:12 AM
CVU home:                     /u01/app/product/12.2.0/crs/
User:                         grid

使用grid用戶執(zhí)行crsctl check ctss命令來查看CTSS的運(yùn)行模式，命令結(jié)果顯示為觀察模式

[grid@jytest1 ~]$ crsctl check ctss
CRS-4700: The Cluster Time Synchronization Service is in Observer mode.

[grid@jytest2 ~]$ crsctl check ctss
CRS-4700: The Cluster Time Synchronization Service is in Observer mode.

現(xiàn)在刪除集群節(jié)點(diǎn)中的第三方時(shí)間同步服務(wù)

[root@jytest1 ~]# rm -rf /etc/ntp.conf
[root@jytest1 ~]# rm -rf /etc/chrony.conf
[root@jytest1 ~]# rm -rf /var/run/chronyd.pid


[root@jytest2 ~]# rm -rf /etc/ntp.conf
[root@jytest2 ~]# rm -rf /etc/chrony.conf
[root@jytest2 ~]# rm -rf /var/run/chronyd.pid

再次檢查CTSS的運(yùn)行模式，可以看到CTSS從觀察模式變?yōu)榱酥鲃?dòng)模式

[grid@jytest1 ~]$ crsctl check ctss
CRS-4701: The Cluster Time Synchronization Service is in Active mode.
CRS-4702: Offset (in msec): 100
[grid@jytest1 ~]$ cluvfy comp clocksync -n all

Verifying Clock Synchronization ...PASSED

Verification of Clock Synchronization across the cluster nodes was successful.

CVU operation performed:      Clock Synchronization across the cluster nodes
Date:                         Mar 3, 2018 1:14:39 AM
CVU home:                     /u01/app/product/12.2.0/crs/
User:                         grid

[grid@jytest2 ~]$ crsctl check ctss
CRS-4701: The Cluster Time Synchronization Service is in Active mode.
CRS-4702: Offset (in msec): 0
[grid@jytest2 ~]$ cluvfy comp clocksync -n all

Verifying Clock Synchronization ...PASSED

Verification of Clock Synchronization across the cluster nodes was successful.

CVU operation performed:      Clock Synchronization across the cluster nodes
Date:                         Mar 3, 2018 1:15:14 AM
CVU home:                     /u01/app/product/12.2.0/crs/
User:                         grid