What is

Unknown status / error value


Could be also:



The NO_MORE_SYSTEM_PTES bug check has a value of 0x0000003F. This is the result of a system which has performed too many I/O actions. This has resulted in fragmented system page table entries (PTE).


This topic is for programmers. If you are a customer who has received a blue screen error code while using your computer, see Troubleshoot blue screen errors.


Parameter Description


0: system expansion PTE type

1: nonpaged pool expansion PTE type


Size of memory request


Total free system PTEs


Total system PTEs


In almost all cases, the system is not actually out of PTEs. Rather, a driver has requested a large block of memory, but there is no contiguous block of sufficient size to satisfy this request.

Often video drivers will allocate large amounts of kernel memory that must succeed. Some backup programs do the same.


A possible work-around: Modify the registry to increase the total number of system PTEs. If this does not help, remove any recently-installed software, especially backup utilities or disk-intensive applications.

Debugging the problem: The following method can be used to debug bug check 0x3F.

First, get a stack trace, and use the !sysptes 3 extension command.

Then set HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\TrackPtes equal to DWORD 1, and reboot. This will cause the system to save stack traces.

This allows you to display more detailed information about the PTE owners. For example:

0: kd> !sysptes 4

0x2c47 System PTEs allocated to mapping locked pages

VA       MDL     PageCount  Caller/CallersCaller
f0e5db48 eb6ceef0        1 ntkrpamp!MmMapLockedPages+0x15/ntkrpamp!IopfCallDriver+0x35
f0c3fe48 eb634bf0        1 netbt!NbtTdiAssociateConnection+0x1f/netbt!DelayedNbtProcessConnect+0x17c
f0db38e8 eb65b880        1 mrxsmb!SmbMmAllocateSessionEntry+0x89/mrxsmb!SmbCepInitializeExchange+0xda
f8312568 eb6df880        1 rdbss!RxCreateFromNetRoot+0x3d7/rdbss!RxCreateFromNetRoot+0x93
f8363908 eb685880        1 mrxsmb!SmbMmAllocateSessionEntry+0x89/mrxsmb!SmbCepInitializeExchange+0xda
f0c54248 eb640880        1 rdbss!RxCreateFromNetRoot+0x3d7/rdbss!RxCreateFromNetRoot+0x93
f0ddf448 eb5f3160        1 mrxsmb!MrxSmbUnalignedDirEntryCopyTail+0x387/mrxsmb!MRxSmbCoreInformation+0x36
f150bc08 eb6367b0        1 mrxsmb!MrxSmbUnalignedDirEntryCopyTail+0x387/mrxsmb!MRxSmbCoreInformation+0x36
f1392308 eb6fba70        1 netbt!NbtTdiOpenAddress+0x1fb/netbt!DelayedNbtProcessConnect+0x17c
eb1bee64 edac5000      200 VIDEOPRT!pVideoPortGetDeviceBase+0x118/VIDEOPRT!VideoPortMapMemory+0x45
f139b5a8 edd4b000       12 rdbss!FsRtlCopyWrite2+0x34/rdbss!RxDriverEntry+0x149
eb41f400 ede92000       20 VIDEOPRT!pVideoPortGetDeviceBase+0x139/VIDEOPRT!VideoPortGetDeviceBase+0x1b
eb41f198 edf2a000       20 NDIS!NdisReadNetworkAddress+0x3a/NDIS!NdisFreeSharedMemory+0x58
eb41f1e4 eb110000       10 VIDEOPRT!pVideoPortGetDeviceBase+0x139/VIDEOPRT!VideoPortGetDeviceBase+0x1b

If the system runs out of PTEs again after the TrackPtes registry value has been set, bug check 0xD8 (DRIVER_USED_EXCESSIVE_PTES) will be issued instead of 0x3F. The name of the driver causing this error will be displayed as well.

About “What is” service

Many of users are faced with the problem of interpreting errors that occur during the work of operating systems. In some cases, the operating system reports that an error has occurred and displays only an integer error code value. Often it is difficult to even roughly understand the cause of the error from the information given out. Our “what is” service contains a database of errors in Windows, Linux, Macos and Solaris operating systems. The database contains tens of thousands of values. In most cases, the online service will be able to help with the definition of the short name of the error and its detailed description.


Current version of service supports following types of error and status codes:

NTSTATUSMany kernel-mode standard driver routines and driver support routines use the NTSTATUS type for return values. Additionally, drivers provide an NTSTATUS-typed value in an IRP’s IO_STATUS_BLOCK structure when completing IRPs. The NTSTATUS type is defined in Ntdef.h, and system-supplied status codes are defined in Ntstatus.h.
Win32 errorWin32 error codes MUST be in the range 0x0000 to 0xFFFF, although Win32 error codes can be used both in 16-bit fields (such as within the HRESULT type specified in section 2.1) as well as 32-bit fields. Most values also have a default message defined, which can be used to map the value to a human-readable text message; when this is done, the Win32 error code is also known as a message identifier.
HRESULTHRESULT is a data type used in Windows operating systems, and the earlier IBM/Microsoft OS/2 operating system, to represent error conditions, and warning conditions.
The original purpose of HRESULTs was to formally lay out ranges of error codes for both public and Microsoft internal use in order to prevent collisions between error codes in different subsystems of the OS/2 operating system.
HRESULTs are numerical error codes. Various bits within an HRESULT encode information about the nature of the error code, and where it came from.
HRESULT error codes are most commonly encountered in COM programming, where they form the basis for a standardized COM error handling convention.
HTTP Status CodeHypertext Transfer Protocol (HTTP) response status codes. Status codes are issued by a server in response to a client’s request made to the server. It includes codes from IETF Request for Comments (RFCs), other specifications, and some additional codes used in some common applications of the HTTP. The first digit of the status code specifies one of five standard classes of responses. The message phrases shown are typical, but any human-readable alternative may be provided.
errnoInteger value, which is returned by system calls and some library functions in the event of an error to indicate what went wrong. errno is defined by the ISO C standard to be a modifiable lvalue of type int, and must not be explicitly declared; errno may be a macro. errno is thread-local; setting it in one thread does not affect its value in any other thread.
Kern ReturnApple Kernel return codes.
Ipp StatusThe IppStatus constant enumerates the status values returned by the Intel IPP functions, indicating
whether the operation is error-free.
Types of error and status codes

Source code

The service is based on the open source library AllStat. Its sources are available on our git server. We will be grateful for your participation in the finalization of the library and ideas for the development of the service. You can also download ErrorLookup libraries and utilities from our site.