IStorage::Commit method (objidl.h)

Article
10/13/2021

The Commit method ensures that any changes made to a storage object open in transacted mode are reflected in the parent storage. For nonroot storage objects in direct mode, this method has no effect. For a root storage, it reflects the changes in the actual device; for example, a file on disk. For a root storage object opened in direct mode, always call the IStorage::Commit method prior to Release. IStorage::Commit flushes all memory buffers to the disk for a root storage in direct mode and will return an error code upon failure. Although Release also flushes memory buffers to disk, it has no capacity to return any error codes upon failure. Therefore, calling Release without first calling Commit causes indeterminate results.

Syntax

HRESULT Commit(
  [in] DWORD grfCommitFlags
);

Parameters

[in] grfCommitFlags

Controls how the changes are committed to the storage object. See the STGC enumeration for a definition of these values.

Return value

This method can return one of these values.

Return code	Description
S_OK	Changes to the storage object were successfully committed to the parent level. If STGC_CONSOLIDATE was specified, the storage was successfully consolidated, or the storage was already too compact to consolidate further.
STG_S_MULTIPLEOPENS	The commit operation succeeded, but the storage could not be consolidated because it had been opened multiple times using the STGM_NOSNAPSHOT flag.
STG_S_CANNOTCONSOLIDATE	The commit operation succeeded, but the storage could not be consolidated due to an incorrect storage mode. For compound files, the storage may have been opened using the STGM_NOSCRATCH flag, or the storage may not be the outermost transacted level.
STG_S_CONSOLIDATIONFAILED	The commit operation succeeded, but the storage could not be consolidated due to an internal error (for example, a memory allocation failure).
E_PENDING	Asynchronous storage only: Part or all of the data to be committed is currently unavailable.
STG_E_INVALIDFLAG	The value for the grfCommitFlags parameter is not valid.
STG_E_INVALIDPARAMETER	One of the parameters was not valid.
STG_E_NOTCURRENT	Another open instance of the storage object has committed changes. As a result, the current commit operation may overwrite previous changes.
STG_E_MEDIUMFULL	No space left on device to commit.
STG_E_TOOMANYOPENFILES	The commit operation could not be completed because there are too many open files.
STG_E_REVERTED	The storage object has been invalidated by a revert operation above it in the transaction tree.

Remarks

IStorage::Commit makes permanent changes to a storage object that is in transacted mode, in which changes are accumulated in a buffer, and not reflected in the storage object until there is a call to this method. The alternative is to open an object in direct mode, in which changes are immediately reflected in the storage object. An object opened in the direct mode does not require calling IStorage::Commit to make permanent changes in the storage object. Calling the IStorage::Commit method on a nonroot storage opened in direct mode has no effect. Opening a root storage object in direct mode ensures that changes in memory buffers are written to the underlying storage device.

The commit operation publishes the current changes in this storage object and its children to the next level up in the storage hierarchy. To undo current changes before committing them, call IStorage::Revert to roll back to the last-committed version.

Calling IStorage::Commit has no effect on currently opened nested elements of this storage object. They remain valid and can be used. However, the IStorage::Commit method does not automatically commit changes to these nested elements. The commit operation publishes only known changes to the next higher level in the storage hierarchy. Thus, transactions to nested levels must be committed to this storage object before they can be committed to higher levels.

In commit operations, you need to take steps to ensure that data is protected during the commit process:

When committing changes to root storage objects, the caller must check the return value to determine whether the operation has been completed successfully, and if not, that the old committed contents of the IStorage are still intact and can be restored.
If this storage object was opened with some of its items excluded, the caller is responsible for rewriting them before calling commit. Write mode is required on the storage opening for the commit to succeed.
Unless prohibiting multiple simultaneous writers on the same storage object, an application calling this method should specify at least STGC_ONLYIFCURRENT in the grfCommitFlags parameter to prevent the changes made by one writer from inadvertently overwriting the changes made by another.

If the STGC_CONSOLIDATE flag is not supported by a storage implementation, calling IStorage::Commit with STGC_CONSOLIDATE specified in the grfCommitFlags parameter returns the value STG_E_INVALIDFLAG.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps \| UWP apps]
Minimum supported server	Windows 2000 Server [desktop apps \| UWP apps]
Target Platform	Windows
Header	objidl.h
Library	Uuid.lib
DLL	Ole32.dll