Step 1. Allocate a Data Set for the BDT Initialization Stream

You must allocate a data set to contain the BDT initialization stream (or streams) that is discussed in Creating a BDT Initialization Stream. You may allocate this data set using ISPF, the TSO ALLOCATE command, or a batch job (using the IEFBR14 program; see Figure 1 for sample JCL).

The initialization stream is run when the operator starts BDT. It initializes the BDT address space. You may wish to have several initialization streams. If several streams are available then the operator, by warm starting BDT, can easily change the network configuration or select different options.

Note: A BDT subsystem that has both file-to-file and SNA NJE nodes does not require two initialization streams. Both nodes exist in one BDT address space, so only one initialization stream is needed.

Requirements are:

Name: Any name. In Step 1. Write a BDT Start Procedureyou will be directed to specify this name on the BDTIN DD statement of the BDT start procedure.
Size: Customer-determined, depending on the number of initialization statements the data set will contain. The minimum is 16 and there is no maximum. Each initialization statement requires at least one record. (A statement may be continued, requiring more than one record.) Two important factors that affect the size of this data set are the number of comment statements you will use (there is no limit) and the number of remote nodes that your home node will communicate with (one BDTNODE statement is required to specify each remote node, with a limit of 100). The IBM-supplied initialization streams in SYS1.SBDTSAMP have approximately 100 records each.
Organization: The data set may be either sequential or partitioned if it is to contain one initialization stream. The data set must be partitioned if it is to contain more than one initialization stream, and each initialization stream must be a separate member. You can give each member any 3- to 8-character name you want or you can use the form BDTINxx, where xx is any one or two alphanumeric characters. The latter method allows the operator a shorthand way of specifying the member name when starting BDT (see Step 1. Write a BDT Start Procedure for details.)
Record Format: Fixed blocked (FB)
Record Length: 80
Block Size: Any multiple of 80

Figure 1. A Sample DD Statement to Allocate a Data Set for the Initialization Stream. It is contained in SYS1.SBDTSAMP member BDT$ALOC.

//BDTIN    DD  UNIT=3380,VOL=SER=BDTDRV,DISP=(NEW,CATLG),
//             DSN=SYS1.BDT.INITS,SPACE=(CYL,(5,1,54)),
//             DCB=(RECFM=FB,LRECL=80,BLKSIZE=3120)