Sends back a chunk of a backup archive file, maximum length of 1Mb
The numeric ID of the backup record whose files you want to download
The backup part you wish to download. For example, if we have a multi-part archive with the base name test.jpa and six parts (.j01 through .j05 and .jpa) then part_id=2 means that we want to download test.j02 and part_id=6 means that we want to download the last part, i.e. test.jpa. If the backup record is not a multi-part archive just use 1.
Each file is internally divided into 1Mb "segments". This parameter tells the JSON API which "segment" to download.
As a rule of thumb, always start with part_id=1 and segment=1. Then, start incrementing the segment. When you get an "Error reading specified segment" error, increase the part number and start again with segment=1. When you get an "Error reading specified segment" error for the first segment of a given part, you are done reading the backup archive parts of this backup record.
You get base64-encoded raw binary data.