Private strand flush not complete

小灰灰 2022-06-09 06:30 1198阅读 0赞

alert警告日志中发现“Private strand flush not complete”  
oracle support 相关的说明文档

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   <td align="left" colspan="6"><strong>Alert Log Messages: Private Strand Flush Not Complete [ID 372557.1]</strong></td> 
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   <td colspan="3"><em>修改时间</em>01-SEP-2010&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<em>类型</em>PROBLEM&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<em>状态</em>MODERATED</td> 
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**In this Document**  
  [Symptoms][]  
  [Cause][]  
  [Solution][]  
  [References][]

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Platforms: 1-914CU;

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   <td><span><em>This document is being delivered to you via<a rel="nofollow"><u><strong>Oracle</strong></u></a>Support's Rapid Visibility (RaV) process and therefore has not been subject to an independent technical review.</em></span></td> 
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## Applies to: ##

Oracle  **Server**\- Enterprise Edition - Version: 10.2.0.1 to 11.1.0.7 - Release: 10.2 to 11.1  
Information in this document applies to any platform.  
"Checked for relevance on 04-Dec-2007"  
  
  
Private strand flush not complete

## Symptoms ##

"Private strand flush not complete" messages are being populated to the alert log for unknown  
reasons.  
  
ALERT LOG EXAMPLE:  
>>>  
Fri May 19 12:47:29 2006  
Thread 1 cannot allocate new log, sequence 18358  
Private strand flush not complete  
Current log\# 7 seq\# 18357 mem\# 0: /u03/oradata/bitst/redo07.log  
Thread 1 advanced to log sequence 18358  
Current log\# 8 seq\# 18358 mem\# 0: /u03/oradata/bitst/redo08.log  
<<<  
  
  
>>

## Cause ##

The message means that we haven't completed writing all the redo information to the log when we are trying to switch. It is similar in nature to a "checkpoint not complete" except that is only involves the redo being written to the log. The log switch can not occur until all of the redo has been written.  
  
A "strand" is new terminology for**10g**and it deals with latches for redo .  
  
Strands are a mechanism to allow multiple allocation latches for processes to write redo more efficiently in the redo buffer and is related to the log\_parallelism parameter present in 9i.  
  
The concept of a strand is to ensure that the redo generation rate for an instance is optimal and that when there is some kind of redo contention then the number of strands is dynamically adjusted to compensate.  
  
The initial allocation for the number of strands depends on the number of CPU's and is started with 2 strands with one strand for active redo generation.  
  
For large scale enterprise systems the amount of redo generation is large and hence these strands are \*made active\* as and when the foregrounds encounter this redo contention (allocated latch related contention) when this concept of dynamic strands comes into play.  
  
There is always shared strands and a number of private strands .  
  
Oracle 10g has some major changes in the mechanisms for redo (and undo), which seem to be aimed at reducing contention.  
  
Instead of redo being recorded in real time, it can be recorded 'privately' and pumped into the redo log buffer on commit.  
  
Similary the undo can be generated as 'in memory undo' and applied in bulk.

This affect the memory used for redo management and the possibility to flush it in pieces.  
  
The message you get is related to internal Cache Redo File management.  
  
You can disregard these messages as normal messages.  
  
When you switch logs all private strands have to be flushed to the current log before the switch is allowed to proceed.

## Solution ##

These messages are not a cause for concern unless there is a significant gap in seq\# between the "cannot allocate new log" message and the "advanced to log sequence" message.

This issue is infact not a bug and is expected behavior.

In some cases, this message can be resolved by increasing db\_writer\_process value.

[Symptoms]: https://support.oracle.com/CSP/main/article?cmd=show&type=NOT&doctype=PROBLEM&id=372557.1#SYMPTOM
[Cause]: https://support.oracle.com/CSP/main/article?cmd=show&type=NOT&doctype=PROBLEM&id=372557.1#CAUSE
[Solution]: https://support.oracle.com/CSP/main/article?cmd=show&type=NOT&doctype=PROBLEM&id=372557.1#FIX
[References]: https://support.oracle.com/CSP/main/article?cmd=show&type=NOT&doctype=PROBLEM&id=372557.1#REF