Following an I/O operation with a DCB, the control program makes certain status information available to the application program. This status information is a 2 byte exception code, or a 16 byte field of standard status indicators, or both.
Exception codes are provided in the data control block (QISAM), or in the data event control block (BISAM and BDAM). The data event control block is described in the following text, and the exception code lies within the block as shown in Table 1. If a DCBD macro instruction is coded, the exception code in a data control block can be addressed as two 1-byte fields, DCBEXCD1 and DCBEXCD2. QISAM exception codes are described in Table 1. The other exception codes are described in Table 2, Table 2, and Table 1.
Status indicators are available only to the error analysis routine designated by the SYNAD entry in the data control block or the data control block extension. Or, they are available after I/O completion from BSAM or BPAM until the next WAIT or CHECK for the DCB. A pointer to the status indicators is provided either in the data event control block (BSAM, BPAM, and BDAM), or in register 0 (QISAM and QSAM). The contents of registers on entry to the SYNAD exit routine are shown in Table 1, Table 2, and Table 3. The status indicators for BSAM, BPAM, BDAM, and QSAM are shown in Figure 1.