Guardian C Library Calls Reference Manual

Reference to Library Calls
Guardian TNS C Library Calls Reference Manual—128833 3-127
__ns_backup_fopen (supplementary)
Return Value
0 if the operation is successful, -1 if an error occurs.
Usage Guidelines
•
This function is called from the backup process to perform a backup open of the file.
Before calling this function, the primary process must have first called the
__ns_fget_file_open_state function to retrieve the file open state information and
sent the state information through the $RECEIVE facility to the backup process.
•
The variable containing the file state information, not the pointer to the variable,
must be sent through the $RECEIVE facility from the primary process to the backup
process.
•
The backup file open does not perform any fopen function access_mode actions that
create or truncate a file. File creation and truncation actions are not necessary
because these actions were performed by the initial fopen call in the primary
process.
•
If an error occurs, errno is set to one of the following:
•
ENOIMEM, if insufficient memory is available.
•
An fopen function error code, if an error occurs on the file open.
•
A Guardian file system error code, if a file system error occurs. (Error 12 indicates
the backup open cannot obtain the same file number assigned to the primary open.)
•
An error detected in the backup process is not automatically sent to the primary
process. User code must handle such processing.
•
The only meaningful operations on file open state information are retrieving with the
__ns_fget_file_open_state function, starting a backup file open with the
__ns_backup_open function, and copying with an assignment statement or a copy
function from the C run-time library. The results of manipulating components of the
file open state information are undefined.
•
In addition to either the CLARGE or CWIDE library file, you must bind the
CNONSTOP library file into programs that use this function.
•
This function can only be used in the Guardian environment.
•
Refer to the Guardian Programmer’s Guide for complete details on fault-tolerant
programming in C.