Some time ago, when I tested the MEMORY database of SQL Server 2014, I found that if the size of the database exceeded the set maximum memory, Error: 701 occurred in SQL Server.
 
Error message:
 
Error: 701, Severity: 17, State: 123.
There is insufficient system memory in resource pool ‘internal’ to runthis query.
 
At that time, I deleted the database and restarted it. In fact, I could still connect it with DAC when I was out of memory.
 
Here’s what I did:
Default connection failure:

The DAC connection is successful (you can also use SQLCMD DAC):

 
Since the server still had memory resources at that time, It was ok to directly modify the maximum memory:
 
sp_configure ‘show advanced options’, 1;
GO
RECONFIGURE;
GO
sp_configure ‘max server memory’, 4096;
GO
RECONFIGURE;
GO
 
If connected to THE DAC, you can check the status of the system, and the session found some problems can be processed, so there is no need to restart the SQL Server, and problems can be found in a timely manner.
 
 
 

An error occurred while Detach database was running today, DBCC CHECKDB saw the following information from the SQL Server error log:
 
Error: 17053, Severity: 16, State: 1.
LogWriter: Operating system error 21(The device is not ready.)encountered.
Write error during log flush.
Error: 9001, Severity: 21, State: 4.
The log for database ” is not available.Check the event log for related error messages. Resolve any errors and restartthe database.
Error: 823, Severity: 24, State: 2.
The operating system returned error 21(The device is not ready.) to SQLServer during a read at offset 0x000000000de000 in file ‘xx.mdf’. Additional messages in the SQL Server error log and system eventlog may provide more detail. This is a severe system-level error condition thatthreatens database integrity and must be corrected immediately. Complete a fulldatabase consistency check (DBCC CHECKDB). This error can be caused by manyfactors; for more information, see SQL Server Books Online.
 
According to error 21, there should be a disk problem, but this disk has a lot of other databases on it that will work, and the newly created files will be fine.
 
Then I saw the error of 823, which should be caused by a hardware error. Microsoft’s recommendation is to run DBCC CHECKDB. But it doesn’t work at all.
 
Trying to run DBCC CHECKDB WITH TABLOCK still reports an error.
 
Then I tried to restart the service once, and the database worked. Running DBCC CHECKDB found no errors.
 
Feel this problem is very bogey, in the hardware disk is no problem even reported disk error.