Why has the system dump setting in fstab if it is not working and need to configure manually?It doesn't make backups/copies automatically, it has to be run manually (or in cron(8) perhaps to automate the process) to create the backups that are regular files. See here:
Why has the system dump setting in fstab if it is not working and need to configure manually?
The fifth field, (fs_freq), is used for these file systems by the dump(8) command to determine which file systems need to be dumped. If the fifth field is not present, a value of zero is returned and dump will assume that the file system does not need to be dumped. If the fifth field is greater than 0, then it specifies the number of days between dumps for this file system.
dump -w)) with /etc/dumpdates to determine if a filesystem needs to be dumped, from dump(8):
-W Tell the operator what file systems need to be dumped. This information is gleaned from the files dumpdates and /etc/fstab. The -W option causes dump to print out, for each file system in the dumpdates file the most recent dump date and level, and highlights those file systems that should be dumped. If the -W option is set, all other options are ignored, and dump exits immediately. -w Is like -W, but prints only those file systems which need to be dumped.