xbackup or xrestore generates a tape group name to take the save. Using the grouping feature provides tape spanning for the saves; using different group names for data, pages, and log allows for different data aging periods for these different types. The group name is generated according to the following rules:
1. "host" is set to the machine name using the command "uname -n".
2. "char" is set to the character "d" for SAVEDATA, "p" for SAVEPAGES, or "l" for SAVELOG and SAVELOGSEG.
3. For a single medium, "group" is set to
${HOST}_${SERVERDB}_${CHAR}.
4. If the medium is a parallel group, a separate group name is generated for each member by appending its number (in the form "_n" or "_nn") to a "$group" set as above.
5. If the "$group" value generated in the steps above would contain more than 23 characters (for any member of the group), the sixth character is removed from "$host". This is repeated as long as the limit is exceeded.
(With the limit of eight characters for "$serverdb", truncation cannot occur for host names that do not exceed nine characters. For a group of at most nine media, a single digit is sufficient, so the host name length extends to ten; for a single medium, it extends to twelve characters. With shorter database names, even longer host names are used without changes.)
Examples:
For machine "6smp", database "ml", action "savelog", a single medium uses the FlashNet group name "6smp_ml_l".
For machine "sillylongname", database "uselimit", action "savedata", the first medium of a ten member group would get the group name "sillylongname_uselimit_d_1". This string has 26 characters, so it is shortened to "sillyname_uselimit_d_1" to keep to the limit. The shortened string uses only 22 characters because the last member gets one more character: "sillyname_uselimit_d_10".
The FlashNet program "dtool" must run with the authority of the UNIX root user. As the database tools (including xbackup) should be run by a normal user, it is necessary to have dtool owned by root with the SetUserID feature. As a FlashNet security provision, it is then necessary to list the user and the tape group in the "groupwd" file, and to list the user and the directory containing the named pipes in the "passwd" file. Please see the FlashNet documentation for details.