One of the client's View databases does not show any sysouts with a archive date from 01/01/2020.
SARBKLST shows tapes from 2 backup generations contain sysouts with archive date 01/01/2020.
When customer request a list of sysout id's and filter on these archive generations, they see some sysout id's belonging to these generations, but with an archive date different from 01/01/2020 (31/12/2019 or 02/01/2020, format dd/mm/yyyy).
The z/OS syslog of 01/01/2020 shows job output gets purged from the JES2 spool, indicating that the View SARSTC has picked up the sysouts from the spool.
After analyzing SMF type 14/15 records generated from Jan 2 2020 06:00, it was determined that there was a SARBCH /DELETE job ran and deleted the reports.
The usual user job generates /DELETE statements to delete obsolete SYSOUTS, and this processing contained a logic error and all outputs from Jan 1 2020 were deleted.
Some Jan 1 reports, that were backed up to tape before the deletion, could be brought back with SARTDR /TADD utility.
The tape from the following backup, however, did not contain reports from Jan 1 2020 16:00 to Jan 2 2020 06:00, so those reports never got backed up to tape, prior to their deletion.