Sql server lock table while updating
It appears that when these run concurrently that they encounter a lock of some kind and it’s preventing the task from finishing and locks up when it goes to update one of the rows.I’m using an exclusive row lock on the rows being read and the lock that shows up on the process is a lck_m_ix lock.I have a C# program that needs to perform a group of mass updates (20k ) to a SQL Server table. In either case, you are doing Begin Transaction, but not setting that transaction to your Command objects doing the updates. Commit(); To check this, while code is running your loop, go to SSMS and do select @@trancount. We need to lock the table since we do validation and updates/inserts as a whole group separately.Since other users can update these records one at a time via an intranet website, we need to build the C# program with the capability of locking the table down. We don't want a record to be validated, then a user use the intranet site to make a change that would cause the record we just validated to suddenly violate a constraint or something.And finally these Update Locks are converted to Exclusive (X) Locks when the data is changed in the third part of the query plan.The question that arrises with this approach is always the same: why does SQL Server acquire Update Locks instead of Shared (S) Locks in the first phase?It has to lock the data in the table itself, and the data any affected indexes, while you perform a modification.In order to improve concurrency, there are several "granularities" of locking that the server might decide to use, in order to allow multiple processes to run: row locks, page locks, and table locks are common (there are more).
As the number of users that access the data increases, it becomes important to have applications that use transactions efficiently.This option has the same effect as setting HOLDLOCK on all tables in all SELECT statements in a transaction. Set the database in single-user mode, make your changes and bring it back online. Change your Transaction Isolation Level to Read Commited (didn't lookup the Enum Value in C# but that should be close).But almost certainly, lock escalation will cause blocking and your users will be pretty much dead in the water (in my experience). When you execute the first update/insert to the table, SQL will start locking and no one will be able to read the data you're changing/adding until you Commit or Rollback thr transaction, provided they are not performing dirty reads (using No Lock on their SQL, or have the connection Isolation level set to Read Uncommited)..Once the table is locked to prevent another user from making any alterations/searches we will then need to preform the requested updates/inserts. Range locks are placed in the range of key values that match the search conditions of each statement executed in a transaction.Since we are processing so many records, we cannot use object seemed to be the best method, however I cannot get the table to lock. If so (or even if not) is there a better method for obtaining a table lock that allows the current program running to search and preform updates? This blocks other transactions from updating or inserting any rows that would qualify for any of the statements executed by the current transaction.
In a relational database, all rules must be applied to the transaction's modifications to maintain all data integrity.