oracle 11 g VKTM detected a time drift？
Tue Dec 26 00:02:25 2017
Archived Log entry 22015 added for thread 1 sequence 13472 ID 0xffffffffffe006b9 dest 1:
Tue Dec 26 01:00:00 2017
Closing scheduler window
Closing Resource Manager plan via scheduler window
Clearing Resource Manager plan via parameter
Tue Dec 26 01:56:23 2017
Thread 1 advanced to log sequence 13474 (LGWR switch)
Current log# 1 seq# 13474 mem# 0: +DATA/erpdb/onlinelog/group_1.261.848792895
Tue Dec 26 01:56:24 2017
Archived Log entry 22019 added for thread 1 sequence 13473 ID 0xffffffffffe006b9 dest 1:
Tue Dec 26 03:11:29 2017
Warning: VKTM detected a time drift.
Time drifts can result in an unexpected behavior such as time-outs. Please check trace file for more details.
Tue Dec 26 03:50:54 2017
Thread 1 advanced to log sequence 13475 (LGWR switch)
Current log# 2 seq# 13475 mem# 0: +DATA/erpdb/onlinelog/group_2.262.848792895
Tue Dec 26 03:50:55 2017
Archived Log entry 22023 added for thread 1 sequence 13474 ID 0xffffffffffe006b9 dest 1:
Tue Dec 26 05:30:23 2017
Warning: VKTM detected a time drift.
Time drifts can result in an unexpected behavior such as time-outs. Please check trace file for more details.
Tue Dec 26 06:02:08 2017
Thread 1 advanced to log sequence 13476 (LGWR switch)
Current log# 5 seq# 13476 mem# 0: +DATA/erpdb/onlinelog/group_5.263.848792895
Tue Dec 26 06:02:09 2017
Archived Log entry 22024 added for thread 1 sequence 13475 ID 0xffffffffffe006b9 dest 1:
Tue Dec 26 06:35:29 2017
Warning: VKTM detected a time drift.
Time drifts can result in an unexpected behavior such as time-outs. Please check trace file for more details.
Tue Dec 26 07:29:09 2017
Thread 1 advanced to log sequence 13477 (LGWR switch)
Current log# 1 seq# 13477 mem# 0: +DATA/erpdb/onlinelog/group_1.261.848792895
Tue Dec 26 07:29:09 2017
Archived Log entry 22025 added for thread 1 sequence 13476 ID 0xffffffffffe006b9 dest 1:^Croot@erpdb1:/u01/oracle/app/oracle/diag/rdbms/erpdb/erpdb1/trace#
2同行回答
该问题和mos上的
Time Drift Detected. Please Check VKTM Trace File for More Details (文档 ID 1347586.1)
很相似，建议查看系统的负载情况和系统配置信息，
The time drifts usually occurring less than 1sec and 5 sec for forward and backward respectively are permissible and OK.
If the traces are emitting time drifts of amount beyond these ranges, then it needs to be analyzed.
Most of the times, during high loads, there would be issues with underlying OS due to virtual memory, network time protocol improper configuration etc.
In general VKTM process need to be scheduled in every 10ms, if due to above reasons this is not happening we see the time drifts and to certain level (mentioned above) are permissible.
Eventually, this probably would cause the resource manager to take improper decisions and can lead to a hang in worst case.
1.MOS中有一篇文档可参考ID 1347586.1
看题主的报错信息，已经影响到了resource manager，可以将相应的trace文件贴出来，查看详细报错。系统负载较高或者内存调度问题都会导致VKTM时间漂移，题主数据库版本是多少?在MOS文档中，Oracle认为这个错误在11.2.0.2到11.2.0.3之间会不断地出现，已经在11.2.0.4版本中被修复。Bug编号为：11837095 "TIME DRIFT DETECTED" APPEARS INTERMITTENTLY IN ALERT LOG, THO' EVENT 10795 SET。
VKTM进程全称为“Virtual Keeper of Time Process”，用于给数据库运行和间隔运算计量提供出一个统一的时间服务。官方解释是：
VKTM acts as a time publisher for an Oracle instance. VKTM publishes two sets of time: a wall clock time using a seconds interval and a higher resolution time (which is not wall clock time) for interval measurements. The VKTM timer service centralizes time tracking and offloads multiple timer calls from other clients.
在11g之前的版本中，如果数据库实例（包括ASM和RAC Instance）需要当前时间的时候，都调用操作系统层面的时间获取函数（例如：gettimeofday()）。进入11g之后，这个动作就由统一的VKTM负责完成，并且在进程内部保留时间过程。其他进程如果需要时间，都通过这个进程间接获得。专门的时间后台进程的出现，最直接的效果就是减少了同操作系统内核的交互，提高了性能。