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The upgrade subsystem in Totara is largely unchanged from Moodle, please review https://moodledev.io/docs/5.0/guides/upgrade for basics of how it works.
Plugin upgrade steps must be reviewed by a dev lead or architect due to previous upgrades which resulted in data loss or which performed poorly, causing the upgrade to overrun the time window allotted to it.
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A customer’s data is the most important and valuable part of their system. |
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The patterns for this are not well-established; we have used adhoc tasks to defer performance intensive upgrades in the past but this has do be done carefully and in small batches to prevent overloading the site on the next cron run. Manual triggers would be preferred
A manual trigger (CLI script or in-product admin action) may also a possibility, with a check API check to detect that the manual upgrade hasn’t runbeen actioned yet.