This feature has different uses in 32 and 64 bit. There's a specific set of AWE API's used to allocate AWE memory. Leaks by these non-SQL components can also cause SQL memory usage to bloat and eventually lead to an OOM (Out Of Memory) condition. This area also includes memory used for COM Objects, CLR Code, Extended Stored Procedures, Large cached plans, etc. The Max Server Memory setting up to SQL 2008 R2 caps only the BPool area.Īll requests for memory greater than 8KB are catered to from the MTL/Non-BPool area. Since the size of a page in SQL is 8KB, this basically means that all data and index page allocation requests are catered to from the BPool, as are Large Pages. The BPool area caters to all memory requests upto 8 KB in size. SQL memory can be divided into 2 parts, BPool and MTL/Non-BPool. This switch is used to fine tune the VAS usage by applications to between 2 and 3 GB, and is added in the boot.ini as well. Keep in mind that setting the /3GB switch means that the OS Kernel can then only "see" up to 16 GB of physical memory.
The /3GB switch changes the default break-up of the VAS, giving 3 GB to applications (such as SQL) which are Large Address Aware, and leaving 1 GB for the OS kernel.
#Sql state 18000 sql error 18456 32 bit#
If you want to utilize more than 4 GB of RAM on a 32 bit server, then you have to use the /PAE switch in the boot.ini OS file. Using 36 bit pointers means that we can now use 36 bit addresses as opposed to 32 bit ones, thereby increasing the max memory the OS can "see" to 64 GB (2^36). Basically, on 32 bit systems, it enables the use of 36 bit pointers (instead of the default 32 bit ones) by utilizing the underlying hardware. This means that each process can potentially grow up to 2 GB in terms of VAS usage. Thus, the VAS on a 32 bit system is 4 GB, of which 2 GB is for the OS Kernel, and 2 GB is allocated to each process. On a 32 bit system, the max address that can be referenced is 2^32 (since each bit can reflect can reflect either a "set" state or a "reset state"), which amounts to ~4 GB.
For details on the need for using Virtual Addresses, please refer to the following technet article:
#Sql state 18000 sql error 18456 windows#
Windows uses Virtual addresses to allocate memory to a process, and the virtual address to physical address mapping is taken care of by the OS. Let’s start off by understanding a few terms: In this post(and others in this series), I shall seek to do a deep dive into SQL Server memory management, and give you as complete a picture as possible.
I know that memory management in SQL Server is one area that’s a bit of an enigma for a lot of people, and most of us only tend to know as much about memory as is related to our day-to-day activities.
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