With arrival of CDC 6600 at CERN in January 1965, there came the first half-inch wide 7-tracks tape units with magnetic tapes at recording densities of 200, 556 and 800 bpi (bytes per inch). By November 1974, there were around 6000 tape reels in the tape library.

Later in March 1972, with CDC 7600 arrival and especially in 1974, 9-track tapes were introduced with densities of 1600 and 6250 bpi and size up to 3600 feet in length.

If the tape was mounted with a write-ring, the user could write on the tape; otherwise it was read-only. The operator would insert the ring according to the mount request unless the tape had a NO RING sticker.

The operations team struggled with frequent errors (around 5%) most likely related to the fact that users could bring in their tapes from outside and worked hard to improve the performance of the whole system (later <1% errors) with managing the tapes inside building 513 (so called "closed shop").

Over the years, the number of tape reels grew to well over 50 000. 

In those days, it was commong to exchange physical tapes with data between institutions (for example for passing salary data to Swiss Bank Corporation

(later UBS AG)).

See also:

CNL 97 (1995)

http://timeline.web.cern.ch/timelines/Computing-at-CERN

http://cdsweb.cern.ch/record/1050339/files/dd-74-35.pdf

http://cdsweb.cern.ch/record/205360/files/p1.pdf

http://cdsweb.cern.ch/record/147113/files/CM-P00059842.pdf

Movie:

https://cdsweb.cern.ch/record/43172