static int DbLog::open(const char *dir, u_int32_t flags, int mode, DbEnv *dbenv, DbLog **regionp);
The DbLog::open method copies a pointer, to the log identified by the directory dir, into the memory location referenced by regionp.
The dir pathname argument is interpreted as described in Berkeley DB File Naming.
If the log region is being created and log files are already present, the log files are recovered and subsequent log writes are appended to the end of the log.
The log is stored in one or more files in the specified directory. Each file is named using the format log.NNNNN, where NNNNN is the sequence number of the file within the log. For further information, see Log File Limits.
The flags and mode arguments specify how files will be opened and/or created if they do not already exist. The flags value is specified by logically OR'ing together one or more of the following values:
All files created by the log subsystem are created with mode mode (as described in chmod(2)) and modified by the process' umask value at the time of creation (see umask(2)))). The group ownership of created files is based on the system and directory defaults, and is not further specified by Berkeley DB.
The logging subsystem is configured based on the dbenv argument. It is expected that applications will use a single DbEnv object as the argument to all of the subsystems in the Berkeley DB package. The fields of the DbEnv object used by DbLog::open are described below. References to the DbEnv object are maintained by Berkeley DB, so it is necessary that the object and memory it references be valid until the object is destroyed. Any of the DbEnv fields that are not explicitly set will default to appropriate values.
The following fields in the DbEnv object may be initialized, using the appropriate set method, before calling DbLog::open:
If lg_max is 0, a default value of 10Mb. is used.
See Log File Limits for more information.
The DbLog::open method either returns errno or throws an exception that encapsulates an errno on failure, and 0 on success.
The DbLog::open method may fail and throw an exception for any of the errors specified for the following Berkeley DB and C library functions: abort(3), atoi(3), close(3), closedir(3), DbEnv::version, fcntl(3), fflush(3), fprintf(3), free(3), fstat(3), fsync(3), getenv(3), getpid(3), getuid(3), isdigit(3), DbLog::unlink, lseek(3), malloc(3), memcpy(3), memset(3), mmap(3), munmap(3), open(3), opendir(3), pstat_getdynamic(3), read(3), readdir(3), realloc(3), shmat(3), shmctl(3), shmdt(3), sigfillset(3), sigprocmask(3), snprintf(3), stat(3), strchr(3), strerror(3), strlen(3), strncmp(3), sysconf(3), unlink(3), vfprintf(3), vsnprintf(3), and write(3). In addition, the DbLog::open method may fail and throw an exception or return errno for the following conditions:
The DB_THREAD flag was specified and spinlocks are not implemented for this architecture.
The specified file size was too large.