You identify records in BDAM data sets by a block reference, a physical key (keyed data set), or a deblocking argument (blocked-data set). The record identification (in the RIDFLD option) has a subfield for each item. These subfields, when used, must be in the above order.
The 2-byte TT begins at relative track zero. The 1-byte R begins at relative record one.
The system programmer must specify the type of block reference you are using in the RELTYPE operand of the DFHFCT TYPE=FILE system macro that defines the data set.
You only need this if the data set has been defined to contain recorded keys. If used, it must immediately follow the block reference. Its length must match the length specified in the BLKKEYL operand of the DFHFCT TYPE=FILE system macro that defines the data set.
You only need this if you want to retrieve specific records from a block. If used, it must immediately follow the physical key (if present) or the block reference. If you omit it, you retrieve an entire block.
The deblocking argument can be a key or a relative record number. If it is a key, specify the DEBKEY option on a READ or STARTBR command and make sure its length matches that specified in the KEYLEN operand of the DFHFCT TYPE=FILE system macro. If it is a relative record number, specify the DEBREC option on a READ or STARTBR command. It is a 1-byte binary number (first record=zero).
Figure 80 shows examples of the following possible forms of BDAM record identifiers. The examples assume a physical key of four bytes and a deblocking key of three bytes: