You can face the performance issue while running alter table on a very huge table having many indexes created.
for example : alter table takes around 38 hours for a very large table which has around 538 columns and 15 nonclustered indexes.
The table size is approx 600 GB having 7.5 millions of rows .
The reason for the performance issue is because the indexes are created serially.
To fix this performance issue, Please follow the below steps :
1. drop the indexes,
2. run the alter table,
3. recreate the indexes in parallel
Hope this will be helpful.
