通过Aeron Archive的API，可以使用以下代码段扩展现有录制：

archive.tryExtendRecording(extendPosition, streamId, sourceIdentity);

其中，extendPosition是扩展录制的初始位置，streamId是录制的数据流ID，sourceIdentity是录制数据的源。

如果扩展录制成功，将返回扩展录制的新记录ID。如果扩展失败，将返回零。

以下是一个完整的代码示例：

public static void tryExtendRecording(AeronArchive archive, long position, int streamId, String sourceIdentity) {
    final Publication publication = archive.addRecordedExclusivePublication(streamId, position);

    if (publication == null) {
        System.out.println("Unable to extend recording, no image available");
        return;
    }

    final long recordedId = archive.tryExtendRecording(position, streamId, sourceIdentity);

    if (recordedId == Aeron.NULL_VALUE) {
        System.out.println("Unable to extend recording");
        return;
    }

    try (Subscription subscription = archive.replay(recordedId, 0, AeronArchive.NULL_LENGTH, sourceIdentity)) {
        final Image image = subscription.imageAtIndex(0);
        final MutableDirectBuffer buffer = new UnsafeBuffer(ByteBuffer.allocateDirect(1024));
        int messages = 0;

        while (image.poll(buffer, 0, buffer.capacity()) > 0) {
            messages++;
        }

        System.out.println("Replayed " + messages + " messages at " + image.position());
    }

    System.out.println("Extended recording to " + recordedId + " at " + position);
}