error exit 20

[Lena M]

we are using rsync version  2.4.6 to perform backups  to our backup
servers. All machines are  running Solaris 2.6 and are located on the
same network. From time to time rsync fails, and we get an error exit
with a status 20. Does anybody know what that means and how  we can
avoid this problem?

Thank you. Your help will be greatly appreciated.

Lena