问题
I have an isolated Azure SQL test database that has no active connections except my development machine through SSMS and a development web application instance. I am the only one using this database.
I am running some tests on a table of ~1M records where we need to do a large UPDATE to data in nearly all of the ~1M records.
DECLARE @BatchSize INT = 1000
WHILE @BatchSize > 0
BEGIN
UPDATE TOP (@BatchSize)
[MyTable]
SET
[Data] = [Data] + ' a change'
WHERE
[Data] IS NOT NULL
SET @BatchSize = @@ROWCOUNT
RAISERROR('Updated %d records', 0, 1, @BatchSize) WITH NOWAIT
END
This query works fine, and I can see my data being updated 1000 records at a time every few seconds.
Performing additional INSERT/UPDATE/DELETE commands on MyTable seem to be somewhat affected by this batch query running, but these operations do execute within a few seconds when ran. I assume this is because locks are being taken on MyTable and my other commands will execute in between the batch query's locks/looping iterations.
This behavior is all expected.
However, every so often while the batch query is running I notice that additional INSERT/UPDATE/DELETE commands on MyTable will no longer execute. They always time out/never finish. I assume some type of lock has occurred on MyTable, but it seems that the lock is never being released. Further, even if I cancel the long-running update batch query I can still no longer run any INSERT/UPDATE/DELETE commands on MyTable. Even after 10-15 minutes of the database sitting stale with nothing happening on it anymore I cannot execute write commands on MyTable. The only way I have found to "free up" the database from whatever is occurring is to scale it up and down to a new pricing tier. I assume that this pricing tier change is recycling/rebooting the instance or something.
I have reproduced this behavior multiple times during my testing today.
What is going on here?
回答1:
Scaling up/down the tier rollback all open transactions and disconnect server logins.
About what you are seeing it seems is lock escalation. Try to serialize access to the database using sp_getapplock. You can also try lock hints.
来源：https://stackoverflow.com/questions/49057593/why-is-my-azure-sql-database-table-permanently-locked