SHOWCB—Display fields of a request parameter list

The format of the SHOWCB macro used to display fields in a request parameter list is:

[label]

SHOWCB

RPL=address
,AREA=address
,LENGTH=abs expression
,FIELDS=([ACB][,AIXPC][,AREA][,AREALEN]
[,ARG][,ECB][,FDBK][,FTNCD]
[,KEYLEN][,MSGAREA]
[,MSGLEN]
[,NXTRPL][,RBA]
[,RECLEN]
[,RPLLEN]
[,TRANSID]
[,XRBA])

The subparameters of the SHOWCB macro can be expressed as absolute numeric expressions, as character strings, as codes, as expressions that generate valid relocatable A-type address constants, in register notation, as S-type address constants, and as indirect S-type address constants. Subparameters with GENCB, MODCB, SHOWCB, and TESTCB, further defines these operand expressions.

label: specifies 1 to 8 characters that provide a symbolic address for the SHOWCB macro.
RPL=address: specifies the address of the request parameter list whose fields are displayed. If you used the RPL macro with a label, you can specify the label here. The RPL parameter is optional when you want to display the length of a request parameter list (FIELDS=RPLLEN). (All VSAM request parameter lists have the same length, so you need not specify the address of a particular one.)
AREA=address: specifies the address of a return area you supply for VSAM to display the contents of the fields specified in the FIELDS parameter. The contents of the fields are displayed in the order specified. The area must begin on a fullword boundary.
LENGTH=abs expression: specifies the length, in bytes, of the return area you provide for VSAM to display the indicated fields in. Each request parameter list field requires a fullword. If the area is not large enough for all the fields, VSAM does not display any of their contents and returns an error code (see Control block manipulation macro return and reason codes).
FIELDS=([ACB][,AIXPC][,AREA][,AREALEN][,ARG]
[,ECB][,FDBK][,FTNCD][,KEYLEN]
[,MSGAREA][,MSGLEN]
[,NXTRPL][,RBA][,RECLEN]
[,RPLLEN][,TRANSID]
[,XRBA][,TRANSID]): specifies the fields whose contents are displayed. Table 1 explains the subparameters you can code in the FIELDS parameter for a request parameter list.

Table 1. FIELDS Keyword Subparameters for a Display Request Parameter List
Subparameter	Fullwords	Description of the Field
ACB	1	Address of the access method control block that relates the request parameter list to the data.
AIXPC ¹	1	Number of alternate index pointers.
AREA	1	Address of the return area the program uses to process a data record for the access as defined by the request parameter list.
AREALEN	1	Length of the return area whose address is given in AREA.
ARG	1	Address of the field containing a search argument, if search arguments are being used.
ECB ¹	1	Address of an event control block, if any, in which VSAM indicates the completion of requests defined by the request parameter list.
FDBK ¹	1	Reason code that VSAM puts into the feedback field to describe the error detected for the preceding request. (The meaning of this code depends on the contents of register 15, which indicates whether the request was successful or failed because of a logical or physical error. See Record management return and reason codes.)
FTNCD ¹	1	Code that describes the function in which a logical or physical error occurred; indicates whether the upgrade set may have been modified incorrectly by the preceding request. (The meaning of this code depends on the contents of register 15, which indicates whether the request was successful or failed because of a logical or physical error. See Record management return and reason codes.)
KEYLEN	1	Length of the search argument, if a generic key is used for a search argument.
MSGAREA ¹	1	Address of the area, if any, into which VSAM puts physical error messages.
MSGLEN	1	Length of the message area, if any.
NXTRPL	1	Address of the next request parameter list, if another one is chained to this one.
RBA ¹	1	Relative byte address of the most recently processed record; you could use it to record the RBAs of records that you are retrieving or storing sequentially or by key.
RECLEN ¹	1	Length of the data record, access to which is defined by the request parameter list.
RPLLEN	1	Length of a request parameter list.
TRANSID	1	Number that relates modified buffers in a buffer pool; described in z/OS DFSMS Using Data Sets.
XRBA ¹	2	The return area (you are providing for VSAM for display) is two full words long to contain values possibly greater than 4GB.

Note:

These fields are significant only if the requests are completed. Therefore, you must wait until the request completes (for example, by issuing a CHECK if the request is asynchronous) before issuing SHOWCB.