ACCESS_METHODS_DATASET_PARENT Problem We had an AlwaysOn Async replica
we had some problems so we deleted the availability group
After that the database and CPU seem to work abnormally
It's very slow and we have waittype = LATCH_EX , ACCESS_METHODS_DATASET_PARENT
We didn't have such a problem till today
Can anybody help ?????
Given the wait types of LATCH_EX and ACCESS_METHODS_DATASET_PARENT I highly doubt AlwaysOn was the culprit.

These two latch types may go hand in hand. You'll want to investigate where the latch_ex waits are actually happening - sys.dm_os_latch_stats may help here where the latch_class is not 'buffer'.

Given that removing AlwaysOn did not help with the situation, I highly doubt AlwaysOn was the problem. However, AlwaysOn may have contributed to some wait time though how much is impossible to say, though I doubt it would be noticeable against your current top waits.

Paul has some information on these:
https://www.sqlskills.com/help/latches/access_methods_dataset_parent/
https://www.sqlskills.com/help/waits/latch_ex/

Additionally this whitepaper on latch contention may be helpful:
http://download.microsoft.com/download/B/9/E/B9EDF2CD-1DBF-4954-B81E-82522880A2DC/SQLServerLatchContention.pdf