Please Check VKTM Trace File for More Details (文档 ID 1347586.1)

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本文档针对Oracle 11.2.0.2及后续版本中出现的VKTM时间漂移警报日志问题进行了说明。该问题通常由高负载下操作系统层面的因素引起，如虚拟内存不足或网络时间协议配置不当等。文档提供了具体解决方案，包括下载并应用补丁11837095以及设置事件10795来限制日志条目。

Applies to:

Oracle Database - Enterprise Edition - Version 11.2.0.2 and later
Information in this document applies to any platform.

Goal

Below message keeps repeating in Alert-log.

Time drift detected. Please check VKTM trace file for more details.

Warning: VKTM detected a time drift

This note explains the possible cause and if the issue needs to be addressed or not.

Solution

There are multiple bugs filed for this issue, Some of them follows:

Bug 12601857 - TIME DRIFT DETECTED. PLEASE CHECK VKTM TRACE FILE FOR MORE DETAILS.
Bug 12374867 - TIME DRIFT DETECTED. PLEASE CHECK VKTM TRACE FILE FOR MORE DETAILS.

Which were closed as duplicates of:

Bug 11837095 "TIME DRIFT DETECTED" APPEARS INTERMITTENTLY IN ALERT LOG, THO' EVENT 10795 SET.

To fix the issue, please download and apply patch 11837095 as available for your release/platform. This is available for 11.2.0.2 and above.

NOTE:
Patch 11837095 extends to functionality of event 10795 (set to level 2) for VKTM tracing and limits alert log entries.

After applying the patch, enable event 10795 at level 2:

alter system set event="10795 trace name context forever, level 2" scope=spfile;

Then bounce the instance (shutdown then startup) for the event to be applied.

The permanent fix is planned to be included in the 11.2.0.4 and 12.1 releases.

For version 11.2.0.1, Apply patch for Bug 9843304 . This Bug is already fixed in 11.2.0.2

Meaning and technical Impact of the error:

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.

VKTM process trace file can be found under bdump, However in this case the trace file doesn't contain useful information, Which makes the message ambiguous.

There are bugs for the VKTM process malfunction

Unpublished Bug 18390507 : EXADATA: VKTM CONSUMING HUGE CPU AFTER PATCHING 11.2.3.3.0 AND 11.2.0.4.3
This Bug is closed as duplicate of Unpublished Bug 18499306

Unpublished Bug 18499306 : DBMX28 DATABASE VKTM PROCESSES CONSUME LARGE AMOUNT OF CPU, UNSTABLIZE MACHINE
This Bug is fixed in 12.2

So please download & apply patch 18499306, if its available on top of your database version for your platform

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