Example of using LMPEO, BUFFLST, and USERRH

The example contained in Figure 1 shows the results of a SEND OPTCD=(LMPEO,BUFFLST,USERRH) in which the application program has specified a buffer list of 12 entries, pointing to 12 discontiguous data areas. For some of the data, the application program wishes to define the RU boundaries. For the rest of the data, VTAM® splits the data into RUs based on a maximum RU size of 100 bytes, which was obtained from the appropriate maximum RU size field in the BIND.

Buffer-list entries 1 and 2 point to data that is split by VTAM. Entry 1 has the initial RH. Because the RH specifies MIC, all three generated RUs are marked as MIC. This chain is assumed to have been started by a previous SEND. Even though entry 2 does not explicitly end the RU, VTAM recognizes that because entry 3 begins another RU, entry 2 must end the current RU.

Entry 3 points to a single RU. This data is not split and is not accumulated with data associated with another entry. Entry 3 has the RH, and is sent as MIC.

Entry 4 points to another single RU. It is handled the same as the preceding entry. Entry 4 has the RH, and is sent as MIC.

Entries 5, 6, and 7 point to data that is accumulated into a single RU. The RU is sent as MIC. Entry 5 has the RH. Entry 7 explicitly ends the current RU. This allows VTAM to recognize that entry 8 begins a new RU.

Entries 8 and 9 point to data that is split by VTAM. Entry 8 has the initial RH. Because the RH specifies MIC, both RUs are marked as MIC. Entry 9 explicitly ends this RU. This is optional because entry 10 begins a new RU.

Entries 10 and 11 point to data that is accumulated by VTAM into a single RU. Entry 10 has the RH. The data is combined into a single RU and sent as MIC. The application program defines this RU in such a way that it exceeds the maximum allowed RU size for the session. Although VTAM does not prevent this, it is a violation of the RU size agreement reached by the two LUs when the session was established, and should not be done by the application program. Depending upon the action taken by the other LU in the session, unpredictable results can occur.

Entry 12 points to data that is split by VTAM. Entry 12 contains the initial RH. Because the RH specifies LIC, the first RU is marked as MIC, and the next (last) RU is marked as LIC.