By default, the backup copy of the transaction log file has the same name as the online file. For each backup operation, you must assign a different name or location for the backup copy, or you must move the backup copy before the next backup is done.
You can make a repeatable incremental backup command by renaming the backup copy of the transaction log.
Use the MATCH keyword in the BACKUP statement. For example, the following statement makes an incremental backup of the transaction log to the directory c:\backup. The backup copy of the transaction log is called YYMMDDxx.log, where YYMMDD is the date and xx is a counter, starting from AA.
BACKUP DATABASE DIRECTORY 'c:\\backup' TRANSACTION LOG ONLY TRANSACTION LOG RENAME MATCH;
Supply the -n option to dbbackup. For example, the following command makes an incremental backup of the sample database, renaming the backup copy of the transaction log.
dbbackup -c "UID=DBA;PWD=sql;DBN=demo" -r -t -n c:\backup
The backup copy of the transaction log is named YYMMDDxx.log, where YY is the year, MM is the month, DD is the day of the month, and xx runs from AA to ZZ, incrementing if there is more than one backup per day. The YYMMDDxx.log file names are used for distinguishability only, not for ordering.