Receiving Data from a READ

See Selecting the Buffer Format for a description of the buffer format options and their performance considerations.

The requested list entry information returns to you in the following output areas:

Buffers specified by BUFFER or BUFLIST
The storage area specified by ADJAREA
The LAARLRMLCTLS field in the answer area specified by ANSAREA.

The particular layout of the returned list entry information depends on the types of information you have requested:

Data entry information
Adjunct area information
List entry control information
Some combination of these.

To access list entries with data entries of different sizes, you must read the list entry controls for each list entry to determine the size of the associated data entry before accessing it. Therefore, if there are different sized data entries, you should also request list entry controls (TYPE=ECONTROLS) if you request data entry information (TYPE=ENTDATA).

The answer area is mapped by the IXLYLAA macro. The contents of the IXLYLAA field, LAARLRMLCTLS, and the list entry controls returned in output buffers are mapped by the IXLYLCTL macro. See z/OS® MVS™ Data Areas in the z/OS Internet library for a complete listing of the IXLYLAA and IXLYLCTL macros.

For each list entry read, requested types of information are arranged in the output buffer in the following order:

List entry controls
Data entry data (if requested and there is a data entry)
Adjunct area data (if requested and adjunct areas exist).

The order of the returned information in the output buffer is maintained even if you request only two of the three types of information.

The order in which you specify ENTDATA, ADJDATA, or ECONTROLS on the TYPE parameter has no bearing on the order in which information is arranged in the output buffers.

Figure 1 illustrates how list entry information is returned by the READ_LIST request if you provide a single buffer.

As shown in Figure 1:

If adjunct area information is returned, the adjunct area information for the first entry is returned in the ADJAREA field, not in a buffer
If list entry controls are returned, the list entry controls for the first entry are returned in the answer area field mapped by LAARLRMLCTLS, not in a buffer.

If you provide multiple buffers, the information is copied into the buffers in order of ascending buffer number. List entry information that cannot fit in the current continues into the next buffer. As a result, the information for a single list entry could be split between buffers. However, all of the data for a particular list entry is returned in the same READ_LIST invocation. You won't get the list entry controls and adjunct for an entry in one invocation and the data entry information for the entry on another invocation.

Figure 1. Layout of List Entry Information Returned by READ_LIST Request