SQL Server误设置max server memory的处理方法

昨天网上一网友说，由于他同事误将“max server memory”设置为10m后，sql server数据库登录不了，当时我简单测试了一下，今天有空就顺手将整个过程整理一下，记录在此。

在ssms的ui界面设置“max server memory”，即使你设置为10m大小，但是它会“悄悄”默认修改为128m，你用profile跟踪或者设置后会发现，它偷偷“修改”了你的设置值（改为了128m），

exec sys.sp_configure n'max server memory (mb)', n'128'
go
reconfigure with override
go
 
configuration option 'max server memory (mb)' changed from 4096 to 128. run the reconfigure statement to install.

如果你没有注意这些细节，或者不信这个事情，那么也可以用脚本测试一下，如下所示，它提示你这个值（10m）不是一个有效值。

当你对“max server memory”做了错误设置后，那么基本上，任何查询或连接都会出现类似下面这样的错误：

an exception occurred while executing a transact-sql statement or batch. (microsoft.sqlserver.connectioninfo)
 
------------------------------
there is insufficient system memory in resource pool 'internal' to run this query. (microsoft sql server, error: 701)
 
 
 
 
 
 
------------------------------
additional information:
 
a connection was successfully established with the server, but then an error occurred during the pre-login handshake. (provider: tcp provider, error: 0 - 远程主机强迫关闭了一个现有的连接。) (microsoft sql server, error: 10054)
 
for help, click: http://go.microsoft.com/fwlink?prodname=microsoft%20sql%20server&evtsrc=mssqlserver&evtid=10054&linkid=20476
 
------------------------------
远程主机强迫关闭了一个现有的连接。 

你检查数据库的错误日志，就会发现有很多额外信息，摘抄部分如下：

.........................................................
.........................................................
2019-12-24 10:15:32.84 spid53      there is insufficient system memory in resource pool 'internal' to run this query.
2019-12-24 10:15:52.88 spid53      error: 18056, severity: 20, state: 29. (params:). the error is printed in terse mode because there was error during formatting. tracing, etw, notifications etc are skipped.
2019-12-24 10:15:55.89 server      error: 17300, severity: 16, state: 1. (params:). the error is printed in terse mode because there was error during formatting. tracing, etw, notifications etc are skipped.
2019-12-24 10:16:12.70 server       failed allocate pages: fail_page_allocation 1
2019-12-24 10:16:12.70 server  
 
process/system counts                         value
---------------------------------------- ----------
available physical memory                6614454272
available virtual memory                 140726213148672
available paging file                    7776440320
working set                                95432704
percent of committed memory in ws               100
page faults                                   57030
system physical memory high                       1
system physical memory low                        0
process physical memory low                       1
process virtual memory low                        0
2019-12-24 10:16:12.70 server     
memory manager                                   kb
---------------------------------------- ----------
vm reserved                                10652776
vm committed                                  57972
locked pages allocated                        86472
large pages allocated                             0
emergency memory                               1024
emergency memory in use                          16
target committed                             131072
current committed                            144448
pages allocated                               84176
pages reserved                                    0
pages free                                        0
pages in use                                 144432
page alloc potential                         -19912
numa growth phase                                 2
last oom factor                                   1
last os error                                     0
2019-12-24 10:16:12.70 server     
memory node id = 0                               kb
---------------------------------------- ----------
vm reserved                                10652712
vm committed                                  57952
locked pages allocated                        86472
pages allocated                               84176
pages free                                        0
target committed                             131048
current committed                            144424
foreign committed                                 0
away committed                                    0
taken away committed                              0
2019-12-24 10:16:12.70 server     
memory node id = 64                              kb
---------------------------------------- ----------
vm reserved                                       0
vm committed                                     20
locked pages allocated                            0
2019-12-24 10:16:12.70 server     
memoryclerk_sqlgeneral (node 0)                  kb
---------------------------------------- ----------
.........................................................
......................................................... 

要解决这个问题，你需要关闭数据库服务， 然后以单用户模式+最小配置启动数据库实例，然后去修改max server memory参数。 关闭数据库过程中如果遇到一些问题，可以通过重启服务器解决问题（这个要根据具体实际情况决定，有时候不会遇到问题，有时候会遇到一些问题，例如net stop mssqlserver命令卡住，出现service_state[mssqlserver]): stop pending）

注意：如果以单用户模式启动，然后以sqlcmd去连接数据库，就会出现下面错误，所以必须以单用户模式+最小配置启动数据库实例

exec sys.sp_configure 'max server memory (mb)',4096; #根据实际情况设置内存大小。
 
reconfigure
 
go

然后重启sql server实例，问题就解决了。 当然你也可以还原master库的备份到其它测试数据库，然后用还原后master数据库的相关文件替换当前数据库master的相关文件来解决问题。但是那样会相对麻烦，没有这种方法简便、有效！

c:\windows\system32>net stop mssqlserver

the sql server (mssqlserver) service is stopping.

the sql server (mssqlserver) service was stopped successfully.

c:\windows\system32>net start mssqlserver

the sql server (mssqlserver) service is starting.

the sql server (mssqlserver) service was started successfully.

总结

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