__amrc is
a structure defined in stdio.h (when the compile-time
option LANGLVL(EXTENDED) or LANGLVL(LIBEXT) is
in effect) to help you determine errors resulting from an I/O operation.
This structure is changed during system I/O and some C specific error
situations. When looking at __amrc, be
sure to copy the structure into a temporary structure of __amrctype
since any I/O function calls will change the value of __amrc. Figure 1 shows the __amrc structure
as it appears in stdio.h.
Note: __amrc is
not used to record I/O errors in UNIX file system files.
Figure 1. __amrc structure#if __TARGET_LIB__ >= __EDC_LE
typedef struct __amrctype {
#else
typedef struct {
#endif
/* The error or warning value from
* an I/O operation is in __error,
* __abend, __feedback or __alloc.
* Look at the value in __last_op
* to determine how to interpret
* the __code union. */
union { 1
int __error; /* error from OPEN/CLOSE, 2
* GENCB/MODCB/TESTCB/SHOWCB */
struct { /* abend code when errno set to EABEND */
unsigned short __syscode, /* system abend code */
__rc; /* return code */
} __abend; 3
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struct {
unsigned char __fdbk_fill,
__rc, /* reg 15 */
__ftncd, /* function code */
__fdbk; /* feedback code */
} __feedback; 4
struct {
unsigned short __svc99_info,
__svc99_error;
} __alloc; 5
} __code;
unsigned int __RBA; 6
/* RBA value returned by VSAM after *
* an ESDS or KSDS record is written *
* out; for RRDS it is a calculated *
* value from the record number. *
* It may be used in a subsequent *
* call to flocate. */
unsigned int __last_op; 7
/* #defined below */
struct {
unsigned int __len_fill; /* __len + 4 */
unsigned int __len; /* length of msg in __str */
char __str[120]; /* the actual data */
unsigned int __parmr0; /* parameter save area (R0) */
unsigned int __parmr1; /* parameter save area (R1) */
unsigned int __fill2[2]; /* non-printable bytes */
char __str2[64]; /* the actual data */
} __msg; 8
/* error message */
#if __EDC_TARGET >= 0x22080000
unsigned char __rplfdbwd[4]; 9 /* rpl feedback word */
#endif /* __EDC_TARGET >= 0x22080000 */
#if __EDC_TARGET >= 0x41080000
#ifdef __LP64 10
unsigned long __XRBA; /* 8 byte RBA */
#elif defined(__LL)
unsigned long long __XRBA; /* 8 byte RBA */
#else
unsigned int __XRBA1;/* high half of 8 byte RBA */
unsigned int __XRBA2;/* low half of 8 byte RBA */
#endif
/* QSAM to BSAM switch reason */
unsigned char __amrc_noseek_to_seek; 11
/* padding to make amrc 256 bytes */
char __amrc_pad[23];
#endif
} __amrc_type;
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- 1 union {
... } __code
- The error or warning value from an I/O operation is in either __error, __abend, __feedback,
or __alloc.
You must look at __last_op to
determine how to interpret the __code union.
- 2 __error
- __error contains
the return code from the system macro or utility. Refer to Table 1 for further information.
- 3 __abend
- This struct contains the abend code when errno is
set to indicate a recoverable I/O abend. __syscode is
the system abend code and __rc is
the return code. For more information on the abend codes, see the
System Codes manual as listed in z/OS Information Roadmap.
The macros __abendcode() and __rsncode() may
be set to the abend code and reason code of a TSO CLIST or command
when invoked with system().
- 4 __feedback
- This struct is used for VSAM only. The __rc
stores the VSAM register 15, __fdbk
stores the VSAM error code or reason code, and __RBA
stores the RBA after some operations.
- 5 __alloc
- This struct contains errors during fopen() or freopen() calls
when defining files to the system using SVC 99. See
the Systems Macros manual, as listed in z/OS Information Roadmap,
for more information on these fields as set by SVC 99.
- 6 __RBA
- This is the RBA value returned by VSAM after an ESDS or KSDS record
is written out. For a RRDS, it is the calculated value from the record
number. It may be used in subsequent calls to flocate(). The __amrc.__RBA field
is defined as an unsigned int, and therefore will only contain a 4-byte
RBA value. This field will be set to -1 when the RBA is beyond 4GB
in an extended addressable VSAM data set. In this case, the __XRBA field
should be used.
- 7 __last_op
- Contains a value that indicates the last I/O operation being performed
by z/OS® XL C/C++ at
the time the error occurred. These values are shown in Table 1.
- 8 __msg
- This may contain the system error messages from read or write
operations emitted from the BSAM SYNADAF macro instruction.
This field will not always be filled. If you print this field using
the %s format, you should print the string starting
at the sixth position because of possible null characters found in
the first 6 characters. Special messages for PDSEs are contained in
the positions 136 through 184. See the Data Administration manual
as listed in z/OS Information Roadmap for
more information. This field is used by the SIGIOERR handler.
- 9 __rplfdbwd
- Contains feedback information related to a VSAM RLS failure. This
is the feedback code from the IFGRPL control block.
- 10 __XRBA
- This is the 8 byte relative byte address returned by VSAM after
an ESDS or KSDS record is written out. For an RRDS, it is the calculated
value from the record number. It may be used in subsequent calls to flocate().
- 11 __amrc_noseek_to_seek
- Contains the reason for the switch from QSAM (noseek)
to BSAM with NOTE and POINT macros
requested (seek) by the XL C/C++ Runtime Library.
This field is set when system-level I/O macro processing triggers
an ABEND condition. The macro name values (defined in stdio.h)
for this field are as follows:
| Macro |
Definition |
|---|
| __AM_BSAM_NOSWITCH |
No switch was made. |
| __AM_BSAM_UPDATE |
Data set is open for update |
| __AM_BSAM_BSAMWRITE |
Data set is already open for write (or update)
in the same C process |
| __AM_BSAM_FBS_APPEND |
Data set is recfm=FBS and open for append |
| __AM_BSAM_LRECLX |
Data set is recfm=LRECLX (used for VBS data
sets where records span the largest blocksize allowed on the device) |
| __AM_BSAM_PARTITIONED_DIRECTORY |
Data set is the directory for a regular or extended
partitioned data set |
| __AM_BSAM_PARTITIONED_INDIRECT |
Data set is a member of a partitioned data set,
and the member name was not specified at allocation |
Sample program CCNGDI1 (Figure 2) demonstrates
how to print the __amrc structure
after an error has occurred to get information that may help you to
diagnose an I/O error. The program writes to a file until it is full.
When the file is full, the program fails. Following the I/O failure,
the program makes a copy of the __amrc structure,
and prints the number of successful writes to the file, the errno, the __last_op code,
the abend system code and the return code.
Figure 2. Example of printing
the __amrc structure/* this example demonstrates how to print the __amrc structure */
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
int main(void) {
FILE *fp;
__amrc_type save_amrc;
char buffer[80];
int i = 0;
/* open an MVS binary file */
fp = fopen("testfull.file","wb, recfm=F, lrecl=80");
if (fp == NULL) exit(99);
memset(buffer, 'A', 80);
/* write to MVS file until it runs out of extents */
while (fwrite(buffer, 1, 80, fp) == 80)
++i;
save_amrc = *__amrc; /* need copy of __amrc structure */
printf("number of successful fwrites of 80 bytes = %d\n", i);
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printf("last fwrite errno=%d lastop=%d syscode=%X rc=%d\n",
errno,
save_amrc.__last_op,
save_amrc.__code.__abend.__syscode,
save_amrc.__code.__abend.__rc);
return 0;
}
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