Would sql deadlock cause job to hang11/29/2023 ![]() Two or more sessions were waiting to acquire a lock on a resource already locked by another session in the same locking chain. Transaction (Process ID 62) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Once you can say you want to update keys, for example, "1 through 5", then the db engine can define locks on those key values.What are SQL Server Deadlocks & How Do You Fix Them | Redgate Skip to content It needs a relevant index in order to create the lock - and spare the other rows. If you have no indexes at all, the db engine may indeed have no choice but to lock the whole table all the time because it has no basis for locking only a range of rows. To understand why you saw a change, remember that in SQL Server, tables are just logical entities, and indexes are the "real" tables. Then you still might have impact across storage units that might lead to a deadlock. UNLESS you have any other indexes defined on the table. sure, you might always avoid locking too many rows. AND it is the criteria for finding a row to update. If you're saying you have a primary key that is also, perhaps, your clustered index key. This can be necessary if you're updating a range. The engine reserves the right to "escalate" a lock to a larger set, such as a page or even a whole table. In a perfect world, if you only update one row, indeed it could only hold a row lock and any other row would not be locked. There are multiple kinds of locks in SQL Server, for different "granularities" of data. Please don't refer to clustered organized tables as 'primary key'. Without the deadlock info everything is speculation. If you want an answer about a deadlock, any deadlock, in SQL Server always start by capturing the deadlock graph. There are many more ways deadlocks can occur, but these are the basic ways UPDATE vs UPDATE deadlocks can occur. When concurrent updates occur on a table organized as a clustered index then deadlocks can occur because the application can requests updates explicitly in an order that results in deadlock (Tran 1 updates keys A then B while Tran 2 updates keys B then A). These can deadlock, as the order of acquiring the locks will differ. different WHERE clauses) can use different NC indexes, in different order. Updates that do not use the same predicate (ie. When concurrent updates occur on a heap or a table organized as a clustered index, but there are non-clustered indexes then each update can use one (or more) non-clustered index to locate the candidate rows for the update. All updates will scan the table in the same order (the heap physical allocation order) and all locks will be acquired in the same order. When concurrent updates occur on a heap (a table without a clustered index) if there are no nonclustered indexes to consider then no updates can deadlock. In a table organized as a heap (no clustered index) all scans have to inspect every row to test a predicate. What I can only speculate you're trying to say is the following: ![]() You are mixing logical (primary key) with physical (data page) and the data page also selects additional data that we do not request for is quite literally impossible to parse for me. So if we have a primary key in a table, then will Data Page still select additional data or only that row with the primary key? I know data page also selects additional data that we do not request for. Even if they use incompatible granularities, no deadlock will occur. row) then they will obtain compatible intent locks at the high levels (table(partition), page) and different locks at the low (row) level. If both queries use the same granularity (eg. might be the reason that the other row of the same table was amongst the data locked in the same data page of the first query?.
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