Record type 21 is written when a data set on magnetic tape is demounted. This
record contains statistics for the entire volume during the period
of time that the volume is mounted, regardless of the number of data
sets on the volume being accessed (and regardless of the number of
CLOSE macro instructions issued).
This record contains the volume serial number, device number, unit
type, and tape format. It contains the number of temporary and permanent
read and write errors, START Subchannel (SSCH) instruction, noise
blocks, erase gaps, and cleaner actions.
Note: - The IFHSTATR utility program formats and prints the error-statistics-by-volume
(ESV) information in this record.
- The current record does not describe who requested the amount
or who performed the I/O.
- Record type 21 does not indicate which records are written because
of environmental record editing and printing (EREP).
- If a maximum count is reached, it is no longer increased. A count
at its maximum value indicates at least that number because no record
is written when the counter is full.
- A record type 21 is written, in addition to demount time, any
time the environmental record editing and printing (EREP) program
is run or when EOD is issued. Therefore, more than one type 21 record
may be written for each tape that was mounted.