CompactVirtualHardDisk method of the Msvm_ImageManagementService class

Article
01/07/2021

Compacts a virtual hard disk file. Compacting is the process of freeing unused portions of the virtual hard disk. The virtual hard disk is not automatically mounted. See Remarks for usage restrictions for this method.

Syntax

uint32 CompactVirtualHardDisk(
  [in]  string              Path,
  [in]  uint16              Mode,
  [out] CIM_ConcreteJob REF Job
);

Parameters

Path [in]

Type: string

A fully qualified path that specifies the location of the merging file.

Mode [in]

Type: uint16

Specifies the mode for the compact operation. This must be one of the following values.

Full (0)

Quick (1)

Retrim (2)

Pretrimmed (3)

Prezeroed (4)

Job [out]

Type: CIM_ConcreteJob

A reference to the job (can be Null if the task is completed).

Return value

Type: uint32

This method can return one of the following values.

Completed with No Error (0)
Method Parameters Checked - Job Started (4096)
Failed (32768)
Access Denied (32769)
Not Supported (32770)
Status is unknown (32771)
Timeout (32772)
Invalid parameter (32773)
System is in use (32774)
Invalid state for this operation (32775)
Incorrect data type (32776)
System is not available (32777)
Out of memory (32778)
File not found (32779)

Remarks

Only the following types of virtual hard disks can be used with this method:

Fixed VHDX
Dynamic VHD
Dynamic VHDX
Differencing VHD
Differencing VHDX

Access to the Msvm_ImageManagementService class might be restricted by UAC Filtering. For more information, see User Account Control and WMI.

Examples

The following C# example compacts a virtual hard disk. The referenced utilities can be found in Common utilities for the virtualization samples (V2).

public enum VirtualHardDiskCompactMode
{
    Full = 0,
    Quick = 1,
    Retrim = 2,
    Pretrimmed = 3,
    Prezeroed = 4
}

public static void CompactVirtualHardDisk(string vhdPath, VirtualHardDiskCompactMode compactMode)
{
    ManagementScope scope = new ManagementScope(@"root\virtualization\v2", null);
    ManagementObject imageService = Utility.GetServiceObject(scope, "Msvm_ImageManagementService");

    ManagementBaseObject inParams = imageService.GetMethodParameters("CompactVirtualHardDisk");
    inParams["Path"] = vhdPath;
    inParams["Mode"] = compactMode;
    ManagementBaseObject outParams = imageService.InvokeMethod("CompactVirtualHardDisk", inParams, null);
    if ((UInt32)outParams["ReturnValue"] == ReturnCode.Started)
    {
        if (Utility.JobCompleted(outParams, scope))
        {
            Console.WriteLine("{0} was compacted successfully.", inParams["Path"]);
        }
        else
        {
            Console.WriteLine("Unable to compact {0}", inParams["Path"]);
        }
    }
    else
    {
        Console.WriteLine("Compact {0} returned error {1}", inParams["Path"], outParams["ReturnValue"]);
    }

    inParams.Dispose();
    outParams.Dispose();
    imageService.Dispose();
}

Requirements

Requirement	Value
Minimum supported client	Windows 8 [desktop apps only]
Minimum supported server	Windows Server 2012 [desktop apps only]
Namespace	Root\Virtualization\V2
MOF	WindowsVirtualization.V2.mof
DLL	Vmms.exe

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