I just need something cleared up about savepoint data/Undo persistence
After 4 minutes of heavy updates in memory a savepoint occurs while a small financial update for 10 million has not yet committed.
The log buffers are persisted synchronously to log segments with both committed and uncommitted records quite fast due to log disk requirement and the savepoint waits for its completion.
A lot of data has been changed and has to be persisted with all of its undo to the data volume which is typically slower and has to write many times more data due to the heavy changes over the last 4 minutes. From my understanding this is done at the start of the savepoint before the critical phase
It makes sense the savepoint would need all undo blocks and dirty blocks persisted in the data file but this could take many minutes, more than 30 I imagine.
Alert 28 (Most recent savepoint) by default has low alert at 1 hour, medium alert at 2 hours and a high alert at 5 hours according to note 1977291
Alert 54 (savepoint duration) alerts with low 5 minutes, medium 10 minutes and high 15 minutes but states the critical phase should not be higher than 2 seconds according to note 1977220
This above alerts indicate that a savepoint duration saving dirty blocks to the data volume may take more than 5 minutes
Are people infrequently getting this alert but it goes away or does someone know how Hana avoids saving masses of dirty data blocks during the savepoint?
All help appreciated, aplogies I am still a Hana innocent