DBCCMD expects standard OS linkage conventions, described in the IBM publication MVS Supervisor Services and Macros Manual. The TSO CALL command invokes the called program using these conventions. In particular, Register 1 should point to a parameter list, and other registers to different areas, as follows:
| Register | Description |
|---|---|
| R1 | Pointer to parmlist. |
| R13 | Pointer to a 72-byte save area (will be used). |
| R14 | Return address to calling program. |
| R15 | entry address of DBCCMD. |
Construct the parmlist and argument as follows:
| parmlist: | 1 full word containing address of argument. (Bit 0 should be set to b’1’ to indicate the last parameter.) |
| argument: | +0: 2-byte length of following parmstring. +2: command parmstring, as described earlier. |