Overview 1-7
Write-Protecting a Cassette
IMPORTANT: The cassette log, which contains a history of usage of the cassette, is updated during the unload procedure. If the cassette is write-protected, the cassette log will not be updated and will be inaccurate.
Cassettes can be write-protected by ! sliding the tab on the rear of the cassette to the left so that the hole is open (See Figure 1-3). In this state, data can be read from the cassette but not written to it. To remove write-protection, " slide the tab to the right so that the hole is closed.
Figure 1-3. Write-protecting a cassette
(➊ = Write-protection ON, ➋ = Write-protection OFF)
Life Expectancy of Cassettes
All DDS-certified media are designed to withstand at least 2000 passes. Under optimum environmental conditions (50% relative humidity, 22°C), this is equivalent to about 100 to150 backup operations. The life expectancy takes into account that an area of a cassette may have several passes during a backup, either because streaming (the optimum performance rate where data is sent to the drive at approximately the same speed as it is written to the cassette media) cannot be maintained, or because the backup software package repeatedly accesses certain areas of a cassette.
Certain extreme (worst case) conditions reduce the recommended maximum number of backup operations. These conditions are as follows:
■Environmental conditions — Sustained use at the low end of the humidity specification reduces the cassette life.
