If you enable versioning for a bucket,
POST automatically generates a
unique version ID for the object being added. Amazon S3 returns this ID in the response using the
x-amz-version-id response header.
If you suspend versioning for a bucket, Amazon S3 always uses
null as the version
ID of the object stored in a bucket.
For more information about returning the versioning state of a bucket, see GET Bucket (Versioning Status).
Amazon S3 is a distributed system. If you enable versioning for a bucket and Amazon S3 receives multiple write requests for the same object simultaneously, all of the objects will be stored.
To see sample requests that use versioning, see Sample Request.