Input format control for ISC (DPM-Bn) subsystems

You can use the following DPAGE selection options to format messages and create a message from multiple DPAGEs.

Input DPAGE selection

The OPTIONS=(DNM) parameter on the DIV statement allows for DPAGE selection using data structure name (DSN).

If more than one DPAGE is defined, a DPAGE label must be specified in every DPAGE. If no DPAGE is selected, the message is rejected and an error message is sent to the other subsystem.

If OPTIONS=NODNM and multiple DPAGEs are defined, a conditional test is performed on the first input record. The results of the test (matching the COND= specification with the data) determines which DPAGE is selected for input data formatting. If the condition is not satisfied and all defined DPAGEs are conditional, the input message is rejected and an error message is sent to the other subsystem.

Single transmission chain

For single transmission chains, DPAGEs can be selected using conditional data.

For multiple DPAGE input with single transmission chain, use the OPTIONS=NODNM parameter. The data in the first input record is used to select the first (or only) DPAGE for formatting. If the data supplied does not match any COND= defined, the last defined DPAGE is selected if the COND= is not specified for this DPAGE. If the condition is not satisfied and all defined DPAGEs are conditional, the input message is rejected and an error message is sent to the other subsystem. If the DSN is supplied in the DD header, it is ignored. For any additional DPAGE (more data supplied than defined for the DPAGE selected), the data in the subsequent record is used to select the next DPAGE for formatting.

Multiple transmission chains

For multiple transmission chains, DPAGEs can be selected using DSN or by using a conditional test.

For multiple DPAGE input with multiple transmission chains, use the OPTIONS=DNM parameter. The DSN supplied in the DD header with each chain of the message is used to select the DPAGE for formatting. If no match is found, the message is rejected and an error message (DFS2113) is sent to the other subsystem.

If DSN is supplied in the DD header with each chain (or any chain) of the message and OPTIONS=NODNM is specified on the DIV statement, the DSN is ignored. The data in the first record of each chain is used to select the DPAGE for formatting. If no condition is satisfied and the last defined DPAGE is unconditional (that is, COND= parameter is not specified), this DPAGE is selected for formatting. If the condition is not satisfied and all defined DPAGEs are conditional, the input message is rejected and an error message is sent to the other subsystem.

How conditional and unconditional DPAGEs are specified depends on whether OPTIONS=DNM or OPTIONS=NODNM is specified.

• For OPTIONS=DNM, conditional is specified with a label in the DPAGE statement.
• For OPTIONS=NODNM:
  • To specify conditional, specify the COND= keyword on the DPAGE statement.
  • To specify unconditional, omit the COND= keyword.

MFS supports two input modes: record and stream.

Record mode

In record mode, one record presented to MFS by the ATTACH manager corresponds to one record defined to MFS. Records and fields defined for each record are processed sequentially. Fields must not be split across record boundaries. The data for fields defined in a record must be present in this record to be considered by MFS. If no data exists for fields defined at the end of the record, a short record can be presented to MFS. If the data for a field not at the end of the record is less than the length defined for the corresponding DFLD, or if no data exists for the field, then a field tab separator character must be inserted to show omission or truncation. If no data exists for the entire record, a null or a 1-byte record (containing a single FTAB character) must be present if additional data records follow it. The record can be omitted:

• At the end of the DPAGE for single DPAGE input.
• At end of the DPAGE for multiple DPAGE input with multiple transmission chains.
• At the end of the last DPAGE for multiple DPAGE input with a single transmission chain. The record cannot be eliminated from the DPAGE if data for another DPAGE follows.

Stream mode

In stream mode, record boundaries are ignored and fields can span record boundaries. Data omitted for fields anywhere in the DPAGE must be indicated by an FTAB.

FTABs are not required for the data omitted to the end of the DPAGE:

• At the end of the DPAGE for single DPAGE input.
• At the end of the DPAGE for multiple DPAGE input with multiple transmission chains.
• At the end of the last DPAGE for multiple DPAGE input with single transmission chain. The FTABs cannot be eliminated from the DPAGE if data for another DPAGE follows.

On input to IMS, the ATTACH manager provides for four deblocking algorithms, UNDEFINED, RU, VLVB, and CHAINED ASSEMBLY, which specify the following:

• UNDEFINED or RU specify that one RU is equal to one MFS record processed. IMS TM defaults to the RU algorithm when UNDEFINED is specified in the ATTACH FM header.
• VLVB specifies that one VLVB record is equal to one MFS record processed.
• CHAINED ASSEMBLY specifies that one input chain is equal to a single MFS record processed for the entire DPAGE.

For MFS RECORD mode, use the VLVB deblocking algorithm. For MFS RECORD mode, do not use:

• CHAINED ASSEMBLY, because the entire input chain would be processed as a single MFS record.
• UNDEFINED or RU, because MFS record definitions would be dependent on the size of the RUs.

For the MFS STREAM mode, all deblocking options can be used. In most cases the UNDEFINED and RU algorithms use less buffer space.

Paging requests

Use the FM headers for entering paging requests when using ISC.