Mainframe Access uses IBM's VTAM APPCCMD interface for LU6.2 communication with many of the target server systems, such as CICS, IMS and DB2. When problems arise and an error is reported for LU6.2 communication with one of these systems, the exact conditions of the error are indicated to Mainframe Access as return values from the APPCCMD call. These return values are logged to Mainframe Access' XDBOUT SYSOUT data set and can help you to identify and correct the situation. The following tables summarize the return value information. If you need more information, see the z/OS Communications Server SNA Programmer's LU 6.2 Reference manual for your level of z/OS and VTAM.