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Chapter 3: Backup and RecoveryTape Managementinitialization information (which includes the tape label name) and compares it to the nextlabel in the sequence.Keep track which tape cartridges: Have been used Are to be sent offsite Are to be loaded in the drivesIt is easy to accidentally put the wrong tape cartridge in a drive and destroy the recentbackup or cause the next backup to fail.When you initialize a tape, some programs write an expiration date on the tape. The tapecannot be overwritten by that same program before the expiration date. However, it mightbe overwritten by another program that ignores the tape header.The next section discusses the importance of retention requirements.There are legal requirements that determine data retention. Check with your company’slegal department on complying with federal, state, and local data retention requirements.Complying with these requirements should be discussed with your legal and financedepartments, external auditors, and consultants. The retention requirement should then bedocumented.The practical side of data retention is that you may be unable to realistically restore an oldbackup. If the operating system, database, and the R/3 System have each been upgradedtwice since the backup, it is unlikely that the backup can be restored without excessivecost—if at all.Retention is related to your backup cycle. It is important to have several generations of fullbackups and all their logs because: If the database is corrupted, you will have to return to the last full backup before thedatabase corruption. If the last full backup is corrupted, you will have to return to the previous full backupbefore the corruption or disaster and roll forward using the backup of the logs from thatbackup until the corruption.How far back you go depends on the level of corruption. Since R/3 is an online real-time system, to recover the database from a full databasebackup, you must apply all the logs since that backup. If this is a significant amount oftime, the number of logs could be tremendous. Therefore, the number of logs you mayneed to apply is a practical constraint to how far back you can recover.System Administration Made Easy3–17