System-defined ECPs

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This page lists and describes system-defined extra create parameters (ECPs). The operating system defines these ECPs in the Ntifs.h header file.

These system-defined ECPs attach the specified extra information to the IRP_MJ_CREATE operation on a file. Elements of the file system stack can query the ECPs for the extra information.

Typically, a filter that processes the IRP_MJ_CREATE operation on a file and then passes the file down to filters below it must not attach and spoof any of the system-defined ECPs to the IRP_MJ_CREATE operation on the file.

Similarly, a kernel-mode driver that processes and issues IRP_MJ_CREATE operations on files must not attach and spoof any system-defined ECPs to the IRP_MJ_CREATE operations on the files.

Filter drivers should consider system-defined ECPs to be read-only. You should use them to retrieve information only.

One exception to restricting a filter driver from attaching any of the following system-defined ECPs is when the filter driver implements a layered file system. It does this by owning file objects and by issuing its own IRP_MJ_CREATE operations on files below its filter, in response to the IRP_MJ_CREATE operation on a file that the filter driver services on its own file objects. Such a filter driver should propagate any ECP_LIST context structure lists from the original IRP_MJ_CREATE operation on a file to the IRP_MJ_CREATE operations that the filter driver issues below it. By propagating these ECP lists, the filter driver ensures that any filters below the filter that issues the IRP_MJ_CREATE operations are aware of the context of the original IRP_MJ_CREATE operation.

ECP GUID	ECP context structure and meaning
ECP_TYPE_CLFS_CREATE_CONTAINER	The GUID used to identify the CREATE_REDIRECTION_ECP_CONTEXT ECP context structure. This ECP can be sent to NTFS to insert a new common log file system (CLFS) container during volume mount.
ECP_TYPE_IO_STOP_ON_SYMLINK_FILTER_GUID	The GUID that identifies the IO_STOP_ON_SYMLINK_FILTER_ECP_v0 ECP context structure. This ECP restricts the behavior of IO_STOP_ON_SYMLINK to act on specified reparse tags only.
ECP_TYPE_OPEN_REPARSE_GUID	The GUID that identifies the OPEN_REPARSE_LIST ECP context structure. This ECP supports callers opening specific reparse points without inhibiting reparse behavior for all classes of reparse points.
GUID_ECP_ATOMIC_CREATE	The GUID that identifies the ATOMIC_CREATE_ECP_CONTEXT ECP context structure. This ECP allow certain supplemental operations to be performed on a file atomically during create.
GUID_ECP_CLOUDFILES_ATTRIBUTION	The GUID that identifies the ECP for cloud files attribution.
GUID_ECP_CREATE_REDIRECTION	The GUID used to identify the ECP that can be sent to query the redirection state of a file for a specific create operation.
GUID_ECP_CSV_DOWN_LEVEL_OPEN	The GUID that identifies the CSV_DOWN_LEVEL_OPEN_ECP_CONTEXT ECP context structure. The Cluster Shared Volumes file system (CSVFS) sends this ECP to the Metadata Node (MDS), and contains information about the type of create.
GUID_ECP_CSV_QUERY_FILE_REVISION	The GUID that identifies the CSV_QUERY_FILE_REVISION_ECP_CONTEXT ECP context structure. This ECP can be sent to CSVFS to request a file revision number.
GUID_ECP_CSV_QUERY_FILE_REVISION_FILE_ID_128	The GUID that identifies the CSV_QUERY_FILE_REVISION_ECP_CONTEXT_FILE_ID_128 ECP context structure. This ECP can be sent to CSVFS to request a file revision number.
GUID_ECP_CSV_SET_HANDLE_PROPERTIES	The GUID that identifies the CSV_SET_HANDLE_PROPERTIES_ECP_CONTEXT ECP context structure. This ECP can be sent to CSVFS to set properties on how it should handle IO arriving on this open.
GUID_ECP_DUAL_OPLOCK_KEY	The GUID that identifies the DUAL OPLOCK_KEY_ECP_CONTEXT ECP context structure. Like the OPLOCK_KEY_ECP_CONTEXT structure, DUAL OPLOCK_KEY_ECP_CONTEXT is used to attach an oplock key to the open file request. With DUAL OPLOCK_KEY_ECP_CONTEXT, a parent key can also be set to provide an oplock for a target file's directory.
GUID_ECP_IO_DEVICE_HINT	A GUID that identifies the IO_DEVICE_HINT_ECP_CONTEXT structure. Device hints are used to assist name provider minifilter drivers in tracking a reparse target to new device.
GUID_ECP_NETWORK_APP_INSTANCE	The GUID that identifies the NETWORK_APP_INSTANCE_ECP_CONTEXT ECP context structure. A client application in a failover cluster might have a set of files opened on a node in the cluster. The file objects are tagged to an application by an instance identifier in the NETWORK_APP_INSTANCE_ECP_CONTEXT structure. On failover, a secondary node can validate a client application's access to the opened files with the previously cached application instance identifier.
GUID_ECP_NETWORK_APP_INSTANCE_VERSION	The GUID that identifies the NETWORK_APP_INSTANCE_VERSION_ECP_CONTEXT structure, which is an ECP context for an application to provide its instance ID. This ECP must accompany a NETWORK_APP_INSTANCE_ECP_CONTEXT (GUID_ECP_NETWORK_APP_INSTANCE) to be valid.
GUID_ECP_NETWORK_OPEN_CONTEXT	The GUID that identifies the NETWORK_OPEN_ECP_CONTEXT ECP context structure and is used to attach extra information for network redirectors. This GUID also identifies the NETWORK_OPEN_ECP_CONTEXT_V0 structure for drivers that run on Windows 7 and later versions of Windows and that must interpret network ECP contexts on files that reside on Windows Vista.
GUID_ECP_NFS_OPEN	The GUID that identifies the NFS_OPEN_ECP_CONTEXT structure. The Network File System (NFS) server attaches the NFS_OPEN_ECP_CONTEXT structure to an open file request. The NFS server uses this GUID on any open file request that the NFS server makes to satisfy a client request. The file-system stack can then determine whether NFS_OPEN_ECP_CONTEXT is attached to the open file request. Based on the information in NFS_OPEN_ECP_CONTEXT the file-system stack can determine the client that requested the file to be opened and why.
GUID_ECP_OPEN_PARAMETERS	The GUID that identifies the ECP_OPEN_PARAMETERS ECP context structure. This ECP allows a caller to specify the purpose of the file open without interfering with existing handles and/or opportunistic locks (oplocks) on the file.
GUID_ECP_OPLOCK_KEY	The GUID that identifies the OPLOCK_KEY_ECP_CONTEXT ECP context structure and is used to attach an oplock key to the open file request. The oplock key lets an application open multiple handles to the same stream without breaking the application's own oplock. For more information about oplocks and oplock keys, see Oplock Semantics Overview.
GUID_ECP_PREFETCH_OPEN	The GUID that identifies the PREFETCH_OPEN_ECP_CONTEXT ECP context structure. The prefetcher is an OS component that is tightly integrated with the cache manager and the memory manager to make disk accesses more efficient and therefore improve performance. If other components interfere with the prefetcher, system performance decreases and might deadlock. Therefore, the prefetcher attaches the PREFETCH_OPEN_ECP_CONTEXT structure to a file to communicate that the prefetcher performs an open request on the file. This open request is specified by the Context member of PREFETCH_OPEN_ECP_CONTEXT. Other components, such as, file system filter drivers, can determine whether PREFETCH_OPEN_ECP_CONTEXT is attached to the file and then take appropriate action.
GUID_ECP_QUERY_ON_CREATE	The GUID that identifies the ECP for query file information on create.
GUID_ECP_RKF_BYPASS	The GUID that identifies the RKF_BYPASS_ECP_CONTEXT ECP context structure.
GUID_ECP_SRV_OPEN	The GUID that identifies the SRV_OPEN_ECP_CONTEXT ECP context structure. A server attaches the SRV_OPEN_ECP_CONTEXT structure to an open file request. The server uses this GUID on any open file request that the server makes to satisfy a conditional client request. The file-system stack can then determine whether SRV_OPEN_ECP_CONTEXT is attached to the open file request. Based on the information in SRV_OPEN_ECP_CONTEXT the file-system stack can determine the client that requested that the file be opened and why.
GUID_ECP_TYPE_VETO_BINDING	Identifies the VETO_BINDING_ECP_CONTEXT ECP context structure. This ECP can be used to veto a bind link on the system's boot partition. Available starting in Windows 11, version 24H2.