Multifetch Buffers

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# Multifetch Buffers

Multifetch buffers are needed only for some Adabas commands run using the ACBX direct call interface; they are not needed for any ACB interface direct calls.

A multifetch buffer defines an area in storage to which Adabas can return the record descriptor elements (RDEs) of multifetched records. This buffer is only required by Adabas commands for which the multifetch option has been activated (by setting Command Option 1 to "M"). RDEs are each 16 bytes long.

A record descriptor element (RDE) has the structure shown in the following table.

Format | Length | Content
--- | --- | ---
All fields unsigned integer, right aligned | 4 bytes | Length of this record in record buffer. Records may have different lengths.
4 bytes | Adabas response for this record. If a nonzero response is given, no record is stored in the record buffer.
4 bytes | ISN for this record.
4 bytes | (L9 only) ISN quantity: value count for this descriptor.

When the multifetch option M is set in the Command Option 1 field of an ACBX command, Adabas returns all records being read in the specified record buffer segments, based on the format specifications in the corresponding format buffer segments. For each record buffer segment, the corresponding multifetch buffer segment contains multifetch headers describing the records in the record buffer segment.

For BT or ET commands, a multifetch buffer is not needed if Command Option 1 is set to "M". In this case, the ISN buffer is used to store the ISNs that need to be removed from the hold queue.

When a multifetch buffer is required, a corresponding format and record buffer are expected as well. If they are not provided, Adabas will create dummy format and record buffers (with length zero) to pair with the multifetch buffer. For complete information about the relationships between the different types of ABD or buffer specifications, read Understanding the Different Buffer Types.

Multiple multifetch buffers can be specified for an Adabas direct call. For complete information about multifetch processing, read Multifetch Operation Processing.