<p>This operation initiates a multipart upload. Amazon S3 Glacier creates a multipart upload resource and returns its ID in the response. The multipart upload ID is used in subsequent requests to upload parts of an archive (see <a>UploadMultipartPart</a>).</p> <p>When you initiate a multipart upload, you specify the part size in number of bytes. The part size must be a megabyte (1024 KB) multiplied by a power of 2-for example, 1048576 (1 MB), 2097152 (2 MB), 4194304 (4 MB), 8388608 (8 MB), and so on. The minimum allowable part size is 1 MB, and the maximum is 4 GB.</p> <p>Every part you upload to this resource (see <a>UploadMultipartPart</a>), except the last one, must have the same size. The last one can be the same size or smaller. For example, suppose you want to upload a 16.2 MB file. If you initiate the multipart upload with a part size of 4 MB, you will upload four parts of 4 MB each and one part of 0.2 MB. </p> <note> <p>You don't need to know the size of the archive when you start a multipart upload because Amazon S3 Glacier does not require you to specify the overall archive size.</p> </note> <p>After you complete the multipart upload, Amazon S3 Glacier (Glacier) removes the multipart upload resource referenced by the ID. Glacier also removes the multipart upload resource if you cancel the multipart upload or it may be removed if there is no activity for a period of 24 hours.</p> <p>An AWS account has full permission to perform all operations (actions). However, AWS Identity and Access Management (IAM) users don't have any permissions by default. You must grant them explicit permission to perform specific actions. For more information, see <a href="https://docs.aws.amazon.com/amazonglacier/latest/dev/using-iam-with-amazon-glacier.html">Access Control Using AWS Identity and Access Management (IAM)</a>.</p> <p>For conceptual information and underlying REST API, see <a href="https://docs.aws.amazon.com/amazonglacier/latest/dev/uploading-archive-mpu.html">Uploading Large Archives in Parts (Multipart Upload)</a> and <a href="https://docs.aws.amazon.com/amazonglacier/latest/dev/api-multipart-initiate-upload.html">Initiate Multipart Upload</a> in the <i>Amazon Glacier Developer Guide</i>.</p>

{
  "success": true,
  "data": {
    "id": "abc123",
    "created_at": "2025-01-01T00:00:00Z"
  }
}

{
  "success": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid request parameters"
  }
}