If an Adabas call using the ACBX interface is made that requires buffer specifications, Adabas buffer descriptions (ABDs) must be used. ABDs must not be used when specifying an Adabas call using the classic ACB interface; if an Adabas call using the ACB interface is made that requires buffer specifications, specify the buffers or pointers to the buffers directly in the Adabas call itself. For more information about the ACBX and ACB interface direct calls, read Calling Adabas.
Since Adabas 8, through its ACBX interface, supports segmented buffers (multiple pairs of format and record buffers, or multiple triplets of format, record, and multifetch buffers), the total number of buffers in an ACBX call is not fixed and limited. The individual buffers are no longer described by fields in the ACBX itself (in the way the buffer lengths are defined in the ACB); instead, each buffer has its own Adabas buffer description (ABD) structure that describes what kind of buffer it is, where it is located, what size it is, and other pertinent information.
In mainframe system applications, the addresses of ABDs are specified directly in the Adabas call; in open system applications, the addresses of ABDs are specified in the ABD list associated with the call.
This document describes the structure of an ABD and ABD lists. For information on the defining the buffers themselves, read Defining Buffers.
Using ABDs in an ACBX interface direct call, the buffers used in a direct call can be contiguous or discontiguous. With Adabas 8, you can define ABDs for eight different types of buffers:
Format buffers
Record buffers
Multifetch buffers
Search buffers
Value buffers
ISN buffers
User buffers
Performance buffers (reserved for use by Adabas Review only).
Each Adabas buffer segment is represented by a single ABD, although you can define multiple ABDs of a given type in the same program. Offset 4 (ABDID) in each ABD identifies the type of buffer defined by the ABD.
In an ACBX interface call, there is a one-to-one correspondence between ABD and buffer specifications; each buffer you want to specify must have a corresponding ABD. The buffer can be specified in the ABD itself or referenced by indirect reference.
ABDs can be specified in any sequence in an ACBX interface direct call. However, if an ABD requires a matching ABD of another type, Adabas will match them sequentially. For example, if three format buffer ABDs and three record buffer ABDs are included in the call, the first format buffer ABD in the call is matched with the first record buffer ABD in the call, the second format buffer ABD is matched with the second record buffer ABD, and the third format buffer ABD is matched with third record buffer ABD.
If unequal numbers of match-requiring ABDs are specified, Adabas will generate a dummy ABD (with a buffer length of zero) for the missing ABD. For example, if three format buffer ABDs are specified, but only two record buffer ABDs are specified, a dummy record buffer ABD is created for use with the third format buffer ABD. If you would prefer that the dummy record buffer ABD be used for the second format buffer ABD instead, you must specify the dummy record buffer ABD yourself prior to the record buffer ABD to be used by the third format buffer ABD.
For commands where data in the record buffer is not described by a format specification in the format buffer, no format buffer segments need be specified; if any are specified, they are ignored. This applies to only a few commands; the most prominent of them is OP.
For information about the relationships between different buffer types, read Understanding the Different Buffer Types.
The following table describes the structure of the ABD.
| DSECT Field Name | Field | Control Block Position | Offset | Length (in bytes) | Format |
|---|---|---|---|---|---|
| ABDXLEN | ABD length | 1-2 | 00 | 2 | binary |
| ABDXVER | Version indicator | 3-4 | 02 | 2 | binary |
| ABDXID | Buffer Type ID | 5 | 04 | 1 | alphanumeric |
| ABDXRSV1 | Reserved 1 | 6 | 05 | 1 | binary |
| ABDXLOC | Buffer location flag | 7 | 06 | 1 | alphanumeric/binary |
| ABDXRSV2 | Reserved 2 | 8 | 07 | 1 | binary |
| ABDXRSV3 | Reserved 3 | 9 | 08 | 4 | binary |
| ABDXRSV4 | Reserved 4 | 13 | 0C | 4 | binary |
| ABDXSIZE | Buffer size (allocated length) | 17-24 | 10 | 8 | binary |
| ABDXSEND | Data length to send | 25-32 | 18 | 8 | binary |
| ABDXRECV | Data length received | 33-40 | 20 | 8 | binary |
| ABDXRSV5 | Reserved 5 | 41-44 | 28 | 4 | binary |
| ABDXADR | Indirect address pointer (if ABDXLOC= C'I') | 45-48 | 2C | 4 | alphanumeric |
| --- | Buffer (if ABDXLOC=C' ' or X'00') | 49-n | 30 | user-defined | not applicable |
Each of the fields in the ABD is described in this section, in the order they appear in the ABD structure.
Required. Use this field to specify the length of the ABD. Currently, the value of this field must be 48.
Required. This field identifies the version of the ABD structure. A value of C'G2' in this field indicates that the buffer definition is in the new, extended ABD structure.
Required. Use this field to identify the type of buffer described by the ABD, as shown in the following table:
| ID Setting | Type of Buffer |
|---|---|
| C'F' | Format |
| C'I' | ISN |
| C'M' | Multifetch |
| C'P' | Performance (reserved for use by Adabas Review only) |
| C'R' | Record |
| C'S' | Search |
| C'U' | User |
| C'V' | Value |
This field is reserved and must be set to binary zeros.
Required. Use this field to identify whether the location of the buffer is defined at an indirect address or is defined at the end of the ABD itself. If this field is set to "I" (C'I'), Adabas assumes indirect addressing is specified and will use the address specified in the indirect address pointer field (ABDADDR). In this case the buffer must reside in 31-bit addressable storage in the primary address space.
If this field is blank (C' ') or contains hexadecimal zeros, the buffer must immediately follow the ABD.
This field is reserved and must be set to binary zeros.
This field is reserved and must be set to binary zeros.
This field is reserved and must be set to binary zeros.
Required. Use this field to specify the size of the buffer (in bytes), as it is allocated. A size of zero indicates a dummy buffer, which is treated as if it was not specified at all.
Required. Use this field to specify the length of the data (in bytes) to be sent to Adabas. The maximum value of this field cannot exceed the value set for the buffer size field (ABDSIZE). A buffer is sent to Adabas only if it is an input buffer for the type of command being issued.
Note:
At this time, you must specify the same value for this field as you
specify for the maximum buffer size (ABDXSIZE field). This is a temporary
limitation of Adabas 8, that will be resolved in a future release.
This field specifies the length of the data (in bytes) returned to Adabas. The Adabas router sets this value at the end of call processing. The maximum value of this field will not exceed the value set for the buffer size field (ABDSIZE). A buffer is received from Adabas only if it is an output buffer for the type of command being issued.
This field is reserved and must be set to binary zeros.
If you set the buffer location flag field (ABDLOC) to C'I' (indirect buffer), specify the address of the actual buffer in this field. More than 32 KB of data can now be specified in an Adabas buffer.
If you set the buffer location flag field (ABDLOC) to C' ' (blanks), this field should contain the actual buffer. More that 32 KB of data can be specified in an Adabas 8 buffer using the ACBX interface. For complete information on defining buffers, read Defining Buffers.
The ABD DSECT can be found in member ADABDX of the distributed Adabas SRCE library.
An ABD list is a file containing a list of pointer references to the Adabas buffer descriptions (ABDs) used for a direct call. ABD lists are used only for open systems ACBX direct calls. In the list, one ABD pointer is required for every buffer segment that is needed for the direct call.
ABD lists can include pointers to the ABDs for eight different types of buffers: format, record, multifetch, search, value, ISN, user, and performance buffers. Multiple ABDs of the same type can be specified in an ABD list.
ABDs can be specified in the list in any sequence. However, if an ABD requires a matching ABD of another type, Adabas will match them sequentially. For example, if three format ABDs and three record ABDs are included in the list, the first format ABD in the list is matched with the first record ABD in the list, the second format ABD is matched with the second record ABD, and the third format ABD is matched with third record ABD. If unequal numbers of match-requiring ABDs are listed (for example, if three format ABDs are listed, but only two record ABDs), Adabas will generate a dummy ABD for the missing ABD (in this case a dummy record ABD will be created).
For complete information about the relationships between the different types of ABD or buffer specifications, read Understanding the Different Buffer Types.
