in Arcserve 2000 SP5 a problem was introduced with a build up of change log files in the arcserve directory. This ultimately would lead to eating up the diskspace on the system. These change log files carry information that keeps a record of files which change between backups. They are not needed for backups and restores.

Arcserve 2000 is no longer officially supported anymore by Computer Associates, hence there is no fix. However there is a workaround to avoid  thes changelogs building up.

stop all arcserve services
remove all r*******.CHG in C:\Program Files\ComputerAssociates\ARCserve\Database

edit C:\Program Files\ComputerAssociates\ARCserve\Database\velocis.ini

change

Archiving=1 to Archiving=0 under the [SERVER] section.

Save the file and restart the Arcserve processes.

At other times you may need to maintain the velocis Databases manually. see here

In short it may be necessary to do the following, but remember that initialising databases removes records and you would have to re-merge tapes back into the database if you had to restore from an old tape. 

C:\Program Files\ComputerAssociates\ARCserve

dbcheck -a -L arcserve;admin;secret DBNAME
where DBNAME = asjob asmedia asobject asrhost astape astpdrv astpsdat

dbdefrag -L arcserve;admin;secret DBNAME
where DBNAME = asjob asmedia asobject asrhost astape astpdrv astpsdat

keybuild -k -L arcserve;admin;secret DBNAME
where DBNAME = asjob asmedia asobject asrhost astape astpdrv astpsdat