After working for a while an SQLCLR assembly wont load

Question

I have a user defined aggregate function in an assembly called Watchdog.
I use that function in a stored procedure.
All the sudden after running just fine for a day it throws an error as soon as I try to execute the stored procedure with this error:
Msg 10314, Level 16, State 12, Procedure spwdAutomaticAction, Line 70
An error occurred in the Microsoft .NET Framework while trying to load assembly id 65541. The server may be running out of resources, or the assembly may not be trusted with PERMISSION_SET = EXTERNAL_ACCESS or UNSAFE. Run the query again, or check documentation to see how to solve the assembly trust issues. For more information about this error:
System.IO.FileNotFoundException: Could not load file or assembly 'watchdog, Version=0.0.0.0, Culture=neutral, PublicKeyToken=fffbd94e193b6c65' or one of its dependencies. The system cannot find the file specified.
System.IO.FileNotFoundException:
at System.Reflection.Assembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
at System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
at System.Reflection.Assembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
at System.Reflection.Assembly.Load(String assemblyString)
I have verified that the Watchdog assembly still has PERMISSION_SET = UNSAFE and that the only assembly it references also has it. Why would it say FileNotFoundException?

Answer 1

If SQL Server is the only process (outside of OS) running on the box, and it's 2008 R2 64-bit, you should be able to free up memory for SQLCLR (and other things like OLE DB linked servers that use the multipage memory allocator) by lowering max_server_memory
with sp_configure.
Don't forget to follow that with a "reconfigure" or "reconfigure with override" statement too. You can see how much memory SQL Server is using by querying SQL Server: Memory Manager counters in perfmon. To see how much is  used for SQLCLR I believe
that would be the SQLServer:CLR counter. You can also get an overview of what SQL Server is using for memory with DBCC MEMORYSTATUS. There's also a bunch of sys.dm_os* DMVs that report on memory listed here:
http://technet.microsoft.com/en-us/library/ms176083(v=sql.100).aspx note that SQLCLR memory (in SQL Server 2008 R2) mostly uses the multipage memory allocator. In the sys.dm_os_memory_objects
DMV you can use "where type like '%CLR%' to find memory allocated by SQL Server for SQLCLR.
If SQL Server isn't the only process running outside the box, other processes (like SSIS or SQL Agent jobs) can deprive SQLCLR of memory also, because it's just using memory outside mem_to_reserve in pre-2012 64-bit.
It sounds like (by your error messages here):
10/02/2013 05:38:16,spid71,Unknown,AppDomain 8 (Watchdog.dbo[runtime].7) created.
10/02/2013 05:36:02,spid16s,Unknown,AppDomain 4 (Watchdog.dbo[runtime].3) unloaded.
10/02/2013 05:36:02,spid1s,Unknown,AppDomain 4 (Watchdog.dbo[runtime].3) is marked for unload due to memory pressure.
that when SQLCLR tries to load your assembly (and all of its dependent assemblies) it's taking some large initial memory allocation that there isn't enough available memory for SQLCLR to handle. It may be that the available memory is too fragmented too obtain
the allocation; at that point your only choice is to recycle SQL Server (and/or possibly the OS).
Also, check to see if you have all of the dependent assemblies cataloged (in sys.assemblies) just in case, because the error message is "file not found".
Hope this helps, Bob