User parameters

Some macros that you can issue in AR mode include control parameters, user parameters, or both. Control parameters refer to the macro parameter list, and the parameters whose addresses are in the parameter list. Control parameters control the operation of the macro itself. User parameters are parameters that a user provides to be passed through to a user routine. For example, the PARAM parameter on the ATTACHX macro defines user parameters. The ATTACHX macro passes these parameters to the routine that it attaches. All other parameters on the ATTACHX macro are control parameters that control the operation of the ATTACHX macro.

Note:

User parameters are sometimes referred to as problem program parameters.
Control parameters are sometimes referred to as system parameters or control program parameters.

The macros shown in Table 1 allow a caller in AR mode to pass information in the form of a parameter list (or parameter lists) to another routine. This table identifies the parameter that receives the ALET-qualified address of the parameter list and tells you where the target routine finds the ALET-qualified address.

Table 1. Passing User Parameters in AR Mode
Macro	Parameter	Location of User Parameter List Address
ATTACH/ATTACHX CALL LINK/LINKX XCTL/XCTLX	PARAM,VL=1	AR/GPR 1 contains the address of a list of addresses. When either a 4-bytes-per-entry parameter list or an 8-bytes-per-entry parameter list with PLIST8ARALETS=YES is being used, this list also contains the ALETs associated with those addresses. (See Figure 1 for the format of the 4-bytes-per-entry parameter list when it contains ALETs.)
ESTAEX	PARAM	SDWAPARM contains the address of an 8-byte area, which contains the address and ALET of the parameter list.

When an AR mode caller who is using a 4-bytes-per-entry parameter list passes ALET-qualified addresses to the called program through PARAM,VL=1 on the ATTACH/ATTACHX, CALL, LINK/LINKX, or XCTL/XCTLX macros, the system builds a list formatted as shown in Figure 1. The addresses passed to the called program are at the beginning of the list, and their associated ALETs follow the addresses. The last address in the list has the high-order bit on to indicate the end of the list. For example, Figure 1 shows the format of a list where an AR mode issuer of ATTACHX who is using a 4-bytes-per-entry parameter list has coded the PARAM parameter as follows:

           PARAM=(A,B,C),VL=1

When an AR mode caller who is using an 8-bytes-per-entry parameter list specifies PLIST8ARALETS=YES, the system builds a parameter list with the 8-byte addresses at the beginning of the list and their associated 4-byte ALETs following the addresses.

Figure 1. Sample User Parameter List for Callers in AR Mode iea99alt

For information about linkage conventions, see the chapter in z/OS MVS Programming: Assembler Services Guide.