Last read-time of file

Problem to solve

CTA knows when the tape was last read. This is fine as long as all the files on the tape are read at about the same time.

Use case:

Data are stored and segregated in several tape pools, depending on the project/experiment to which the data belongs. The tapes are then filled more or less continuously in the time period of one day to several months, from the first to the last file on a given tape. The number of files on a single tape usually ranges from several thousand to several hundred thousand. Later, files are read in small quantities, very rarely the entire tape at once.

For this reason, the CTA should provide the following information for each file (for each separate copy, if there are several on separate pages):

• when it was read for the last time; field: last-read-time,
• the number of read attempts; field: read-count,
• the number of failed read attempts since the last successful read of the file; field: read-error-count,
• the number of total failed read attempts; field: read-error-count-absolute.

This would enable operators to monitor the consistency and availability of files by reading them periodically (if a file has not been read for a certain period of time). If a file is not properly readable it is up to operators handle it in some ways.