1/1/2024 0 Comments Sql server deadlock traceflag![]() ![]() Required to be enabled on SQL Server instances with transaction logįile residing on disk with sector size of 512 bytes. Global trace flag, use DBCC TRACEOFF with the -1 argument.Īnd on the definition of flag 1800 it says:Įnables SQL Server optimization when disks of different sector sizesĪre used for primary and secondary replica log files, in SQL ServerĪlways On and Log Shipping environments. Trace flag with DBCC TRACEON is lost on server restart. For example, toĮnable the 2528 trace flag globally, use DBCC TRACEON with the -1Īrgument: DBCC TRACEON (2528, -1). Using the DBCC TRACEON and DBCC TRACEOFF commands. This ensures the traceįlag remains active after a server restart. Startup, by using the -T command line option. ![]() We recommend that you enable global trace flags at The documentation you referenced says that:Ī global trace flag must be enabled globally. If I cannot get this to work, I suppose the intermediate option would be to reformat the log drive on the existing primary to 64KB block size Obviously the way to find out is to test but due to this being a production server, I would need a maintenance window to that which isn't available to me at the momentĮventually, the primary server will be migrated to new hardware and I will ensure the disks are formatted in the same manner but for the tie being I was hoping this traceflag would provide a quick fix. The documentation doesn't reference that a reboot is required. I then checked the error log on the secondary and can see the messages regarding Async IO still persist.ĭoes this traceflag need setting as a startup parameter (with subsequent reboot) to take effect? Obviously I would do this anyway so it persists reboots but just ran the DBCC TRACEON first so it is active With this in mind, I ran DBCC TRACEON (1800, -1) on the primary and verfied it was on with DBCC TRACESTATUS Therefore it seems traceflag 1800 should be enabled on the primary. I have run the following command on both servers: fsutil fsinfo ntfsinfo L:\Īnd can see for the primary: Bytes Per Sector : 512Īnd the secondary: Bytes Per Sector : 512 ![]() With 512-byte sector size as per Microsoft's recommendation This article suggests a fix is to turn on trace flag 1800 on the server The current IO is on file L:\SQLSERVER\Logs\MyDatabase_log.ldf. There have been N misaligned log IOs which required falling back to synchronous IO. The log drive (and other SQL Server drives) on the secondary has been formatted to 64KB block size, whereas the primary server is on the default 4KB.Īs a result of this we are getting the following entries in the log of the secondary almost constantly. We have recently migrated our database mirroring secondary to new hardware. ![]()
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