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# DoAsyncSynchronize

Forces the hardware buffer to flush data blocks to the media.

```
virtual kern_return_t DoAsyncSynchronize(uint32_t requestID, uint64_t lba, uint64_t numOfBlocks);
```

## Parameters

`requestID`

An opaque identifier. After the dext completes the request, it calls [`Complete`](/documentation/BlockStorageDeviceDriverKit/IOUserBlockStorageDevice/Complete) and sends this value as a parameter.

`lba`

The logical block number of the first block to synchronize.

`numOfBlocks`

The number of blocks to synchronize.

## Return Value

A value that indicates the synchronize result. <doc://com.apple.documentation/documentation/DriverKit/kIOReturnSuccess> indicates success. For error definitions, see <doc://com.apple.documentation/documentation/iokit/iokit_constants>.

## Discussion

When the synchronize operation completes, the dext calls your [`Complete`](/documentation/BlockStorageDeviceDriverKit/IOUserBlockStorageDevice/Complete) method with the results of the operation.

---

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