Writing & reading several records to/from a data set w/ multi-byte encoding causes TSO servlet timeout

Using the z/OSMF ReST API, writing 810 or more records to a data set with a multi-byte encoding (such as IBM-937) causes the request to timeout after the given response timeout has elapsed.

1. Create a physical, sequential data set NEW.DATASET with the default block size, lrecl, etc.

2. Given the following request body, prepare a PUT request to the endpoint /zosmf/restfiles/ds/NEW.DATASET
   你好世界你好世界你好世界你好世界你好世界你好世界你好世界你好世界你好世界你好世
   你好世界你好世界你好世界你好世界你好世界你好世界你好世界你好世界你好世界你好世
   你好世界你好世界你好世界你好世界你好世界你好世界你好世界你好世界你好世界你好世
   ...(repeat the sequence above, until you have at least 810 lines)

3. Specify the following headers for the request:
   Content-Type: text/plain; charset=UTF-8
   X-IBM-Data-Type: text;fileEncoding=IBM-937
   X-IBM-Response-Timeout: 300

4. Notice that once the request is sent, the request seemingly hangs until the response timeout has elapsed

5. Once the response timeout has elapsed (default being 30 sec), the following JSON object is returned with a 500 Internal Server Error:

{
  "rc": 4,
  "reason": 1,
  "category": 2,
  "message": "receiveResponseHeader: timeout receiving response (>300 secs): TsoServerConnection(USER=TRAE, ASID=0x007c, QID=0x00260012)"
}

If you adjust the request body so it only uploads 809 lines, the request succeeds without any error within a matter of seconds.

The same issue occurs when reading a data set with 1620 or more lines using the same multi-byte encoding. The only difference for testing this scenario is using GET for the request method instead of PUT, and not including a body with the request.