ORA-27300: OS system dependent operation:fork failed with status: 12

今天查看一用户的alert日志，发现日志中有ora-27300错误，具体错误如下：

Errors in file /opt/app/oracle/admin/orcl/bdump/orcl1_psp0_544938.trc:
ORA-27300: OS system dependent operation:fork failed with status: 12
ORA-27301: OS failure message: Not enough space
ORA-27302: failure occurred at: skgpspawn3
Mon Dec  9 15:20:26 2013
Process PZ15 died, see its trace file
Mon Dec  9 15:20:26 2013
Process startup failed, error stack:
Mon Dec  9 15:20:26 2013
Errors in file /opt/app/oracle/admin/orcl/bdump/orcl1_psp0_544938.trc:
ORA-27300: OS system dependent operation:fork failed with status: 12
ORA-27301: OS failure message: Not enough space
ORA-27302: failure occurred at: skgpspawn3
Mon Dec  9 15:20:27 2013
Process PZ14 died, see its trace file
Mon Dec  9 15:20:27 2013
Process startup failed, error stack:
Mon Dec  9 15:20:27 2013
Errors in file /opt/app/oracle/admin/orcl/bdump/orcl1_psp0_544938.trc:
ORA-27300: OS system dependent operation:fork failed with status: 12
ORA-27301: OS failure message: Not enough space
ORA-27302: failure occurred at: skgpspawn3
Mon Dec  9 15:20:28 2013
Process PZ13 died, see its trace file
Mon Dec  9 18:10:24 2013
Thread 1 advanced to log sequence 14822

这个错误很典型，不同的提示有不同的解决方法， 具体可以看Troubleshooting ORA-27300 ORA-27301 ORA-27302 errors (Doc ID 579365.1)，针对这个错误提示，有如下解释：

Database Cannot Start Due to Lack of Memory (Doc ID 560309.1)

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Modified:02-Mar-2013Type:PROBLEM

In this Document

Symptoms

Cause

Solution

References

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This document is being delivered to you via Oracle Support's Rapid Visibility (RaV) process and therefore has not been subject to an independent technical review.

APPLIES TO:

Oracle Database - Enterprise Edition - Version 10.2.0.1 to 11.2.0.3 [Release 10.2 to 11.2]
Information in this document applies to any platform.
***Checked for relevance on 11-Jan-2012***

SYMPTOMS

The database cannot start up due to the following errors:

*** SERVICE NAME:(SYS$BACKGROUND) 2008-03-24 17:02:34.855 
*** SESSION ID:(1104.1) 2008-03-24 17:02:34.855 
*** 2008-03-24 17:02:34.855 
Process startup failed, error stack: 
ORA-27300: OS system dependent operation:fork failed with status: 12 
ORA-27301: OS failure message: Not enough space 
ORA-27302: failure occurred at: skgpspawn3 
*** 2008-03-24 17:02:38.158 
Process startup failed, error stack: 
ORA-27300: OS system dependent operation:fork failed with status: 12 
ORA-27301: OS failure message: Not enough space 
ORA-27302: failure occurred at: skgpspawn3 

CAUSE

This issue is mainly caused by lack of memory / swap. 
Checking the memory configuration on the server, the following was found:

Total Physical Memory 38912 MB 
Swap: Max Size 17664 MiB 

So, RAM is 38 GB, SWAP space is only 17 GB

SOLUTION

1- We should increase the server swap space (paging space). 
In 11.1 and 10.2, the general rule of thumb is that swap space should be:
RAM                              SWAP
1GB to 2GB                   1.5 times RAM 
> 2GB and <= 8GB          1 times RAM 
> 8GB                            .75 times RAM

In 11.2, it is:
RAM                              SWAP
1GB to 2GB                   1.5 times RAM 
> 2GB and <= 16GB        1 times RAM 
> 16GB                          16GB RAM

So in our case on 10.2, the recommended swap space should be 28 GB  instead of  17 GB 

2- We can also try to increase physical memory, if possible.

3- On Unix Platforms, the user limits  for user oracle should be checked using the "ulimit -a " command.

4- We should also check memory parameters in the pfile/spfile that may add more load to the memory consumption on the server.  For example setting the following parameters can add more overhead to memory consumption 

-  lock_sga=true 
-  db_keep_cache_size=

可以看到，是由于swap设置不规范导致，当然在生产库上重新设置swap有风险，最简单的方式就是设置lock_sga=true,把SGA锁定物理内存里面！！