Disable lightweight pooling
Applies to: 
SQL Server
This rule checks that lightweight pooling is disabled on the server. Setting lightweightpooling to 1 causes SQL Server to switch to fiber mode scheduling. Fiber mode is intended for certain situations in which the context switching of the UMS workers is the important bottleneck in performance. Because this is rare, fiber mode seldom improves performance or scalability on the typical system.
Best practices recommendations
The lightweightpooling option should only be enabled after thorough testing, after all other performance tuning opportunities are evaluated, and when context switching is a known issue in your environment.
We recommend that you don't use fiber mode scheduling for routine operation because it can decrease performance by preventing the regular benefits of context switching, and because some components of SQL Server that use Thread Local Storage (TLS) or thread-owned objects, such as mutexes (a kind of Win32 kernel object), can't function correctly in fiber mode.
To remove lightweight pooling, execute the following statement, and then restart the SQL Server Database Engine.
sp_configure 'show advanced options', 1;
GO
sp_configure 'lightweight pooling', 0;
GO
RECONFIGURE;
GO
For more information
lightweight pooling Server Configuration Option