The following sections present information about the LU 6.2 communications trace and its interpretation.
The BBC LU 6.2 component is responsible for LU 6.2 communications between address spaces (that is, between a CAS and another CAS, between a CAS and a CMAS, or between a CAS and a TSO user). The major portion of BBC resides only in the CAS; the remainder is loaded into any address space that is connected to the CAS.
The BBC LU 6.2 component keeps an internal wrap trace of all LU 6.2 messages sent to and from the CAS. This trace facility is always active and cannot be disabled. When there is a communications problem, such as a TSO user waiting for a response, this trace can be helpful in determining the status of the response. Some of the information that can be found in the communications trace includes:
The BBC LU 6.2 trace entries that you will find in a CAS dump formatted by the interactive problem control system (IPCS) can be viewed using the format described for the BBC LU6.2 Communication display.
The BBC LU 6.2 trace is made up of a X'10'-byte header followed by X'50'-byte table entries. The total length is X'7D10' bytes, which is usually sufficient to determine what, if anything, went wrong.
The format of the trace header is as follows:
Figure 10 is an example of the first X'60' bytes of a BBC LU 6.2 trace:
BBCTRACE
LIST 7F6A52F0 ASID(X'0202') LENGTH(32016) AREA
ASID(X'0202') ADDRESS(7F6A52F0) KEY(48)
7F6A52F0. 00007D10 00000038 00000152 00000190 |..'.............|
7F6A5300. 008DC3C8 7F6A2C68 000005B6 00000000 |..CH"...........|
7F6A5310. 00160000 00000000 00000000 00000000 |................|
7F6A5320. 00000005 00000592 00000000 007212FF |.......k........|
7F6A5330. 00380000 00000000 00000000 00000000 |................|
7F6A5340. 0000D4E5 E2E35AD9 85869985 A288E389 |..MVST!RefreshTi|
To locate the most recent entry, multiply the current entry index by X'50' (entry length) and add it to the first entry address of the table. Using the sample header shown in Figure 10, the following calculation determines the most recent entry in the trace:
X'152' * X'50' = X'69A0' (Offset into the table)
X'7F6A5300' + X'69A0' = X'7F6ABCA0' (Address of most recent entry)
Each trace table entry has the following structure: