QGET FM header format

The following table shows the format of the QGET FM header.

Table 1. QGET FM header format
Byte Bits Name Contents
0   FMHL Length
1 0 FMHC  
1-7 FMHT Type: B'0000110'
2-3   FMH6CMD Command Code: X'0A10'
4   FMH6MOD Modifier
0 FMH6LNSZ B'0' 1-Byte Length Fields
1-6   Reserved
7 QGETLAST B'1' Coded request, get last1
5   FMH6FXCT

Length of Fixed-Length Parameters
(=X'01')
6   QORG Type of paging request
X'00'
Queue organization not specified. Valid on input to IMS.
X'01'
Sequential. Invalid.
X'02'
Linear. Valid on input to IMS if it matches the QORG in the QXFER sent by IMS.2
X'03'
Hierarchic. Not supported by IMS.
X'04' to X'FF'
Reserved
7-m   QNAME Q from which records are retrieved. IMS message ID (ATTDQN/SCDDQN)3
m+1-n   QCURSOR Cursor vector in target queue4
n+1-p   QTRNSZ Size of maximum record to be returned (binary). Ignored by IMS if sent. All fixed-length parameters must be present when you use this header.
Notes:
  1. The QGETLAST selects a logical page whose value is equal to the last logical page in the message.

    The QGET FM header is valid and causes a QXFR reply only if the OLP demand-paged output message is in progress and the cursor value requested is within the range of the output message.

  2. If QORG is invalid, an error message is sent and the output message is returned to the message queue for retransmission.
  3. The QNAME (message identifier) is required on each page for scheduled demand-paged output and is optional for synchronous demand-paged output. If the QNAME parameter is present, it must match the ATTDQN/SCDDQN parameter in the ATTACH FM header sent by IMS. If QNAME is not specified for synchronous demand-paged output, IMS assumes it to be the same as the ATTDQN parameter name. If the QNAME parameter does not match the ATTDQN/SCDDQN parameter, an error message is sent and the output message is returned to the message queue for retransmission.
  4. The cursor vector consists of one 2-byte binary number representing the logical page number. IMS does not support hierarchic retrieval; therefore, the 2-level cursor (logical page number followed by the presentation page number) is invalid and results in an error message being issued. The length value of the QCURSOR is 2. The next 2 bytes contain the logical page number (absolute) request.