Bug in PostgreSQL 15 : Facing error in PG15

Dear Team,

We have upgraded PostgreSQL DB from version 13 to 15 version .
We are facing issue in PG15 we not enable any parameter related to AUTOVACUUM , but still running on PG15 data base.

2313192 | 02:10:01.283176 | | myLava | active | autovacuum: VACUUM ANALYZE public.tstock_movement (to prevent wraparound)

And one more issue we are facing after upgrade lot of alert is coming in DB log file , please suggest this is bug in Postgresql-15 version.

DB OS RHEL8.

2024-08-26 00:00:36.783 IST [702937] WARNING: oldest xmin is far in the past
2024-08-26 00:00:36.783 IST [702937] HINT: Close open transactions soon to avoid wraparound problems.
You might also need to commit or roll back old prepared transactions, or drop stale replication slots.
2024-08-26 00:00:36.784 IST [702937] WARNING: oldest xmin is far in the past
2024-08-26 00:00:36.784 IST [702937] HINT: Close open transactions soon to avoid wraparound problems.
You might also need to commit or roll back old prepared transactions, or drop stale replication slots.

Regards,
Ram Pratap.