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Asked: 2026-05-23T07:26:47+00:00

In my database I have two closely related tables. There is a frequently called

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In my database I have two closely related tables.
There is a frequently called SP that INSERTs some rows into both tables within a transaction, and several other places that do SELECTs from these tables joined.

INSERTs take X locks on both tables, SELECTs take S or IS locks on them. Since the order in which shared locks are taken varies from query to query, some of them occasionally get deadlocked with the INSERT transaction.

Is there any good way to avoid these deadlocks (NOLOCK probably doesn’t qualify as ‘good’)?

So far the only general solution I can think of is using SNAPSHOT isolation level. However, it would add some performance overhead, and I haven’t yet found any sound data on how large this overhead is.

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  1. Editorial Team

    I use snapshot in my system. It is not free, that’s for sure, but the alternatives are not free either – blocking uses up resources too. Using rowlock does not always help.
    Also snapshot gives you a consistent point in time snapshot of your data; otherwise you are exposed to some subtle bugs.

    One more thing: you can get deadlocks even if you have only one table, examples here: Reproducing deadlocks involving only one table

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