SDDLU exit routine parameter list

When the exit gets control, the address of the following parameter list is in register 1.

Table 1. SDDLU exit routine parameter list
Dec (Hex) offset	Size (Bytes)	Description
0 (0)	4	Address of the vector length field This field points to a 2-byte field that identifies the length of the entire vector, including the length of the vector header.
4 (4)	4	Address of vector type field This field points to a 1-byte field that identifies the type of vector that is passed to the exit. Type Description X'05' Dynamic definition request X'06' Begin X'07' End
8 (8)	4	Address of vector data This field points to the vector data that is passed to the exit. When VTAM® calls the exit with a begin or end vector, this field is set to 0.
12 (C)	4	Address of exit work area This field points to an 8-byte field that a user-written exit can use. The default exit does not use this field because it does not allocate storage. VTAM saves the contents of this user field after every successful invocation of the SDDLU exit routine. In this way, the contents are available to the exit routine the next time the routine is called. A discussion on field usage follows: Byte X'00'–X'03' When VTAM calls the exit with a begin vector, the exit allocates storage and places the address of the storage in this field. When VTAM calls the exit with a dynamic definition request vector or an end vector, this field contains the value supplied as output from begin vector processing. X'04'–X'07' These can be used to uniquely identify an exit's level or version. The last 4 bytes are displayed following subsequent use of the DISPLAY EXIT command (see z/OS Communications Server: SNA Operation for information about this command).
16 (10)	4	Address of the parameter string

For activation and deactivation functions, offset X'10' can contain the address of a parameter string if you specify a value for the PARMS operand on the MODIFY EXIT command. The parameter string is only available for vector types BEGIN (X'00') and END (X'FF'). The parameter string is in the form of a 2-byte length field followed by the actual data.