what is the difference between locking and blocking in sql server?
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Locking is the mechanism that SQL Server uses in order to protect data integrity during transactions. Block (or blocking lock) occurs when two processes need access to same piece of data concurrently so one process locks the data and the other one needs to wait for the other one to complete and release the lock.
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Locking is what seen elsewhere as "grayed", you can see objects but can't select or edit them. Invisible is invisible BUT selectable (!?) and kept in Memory. Freezing makes Objects invisible, unselectable AND thrown out of Memory.
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The major difference is that wait() releases the lock or monitor while sleep() doesn't releases any lock or monitor while waiting. Wait is used for inter-thread communication while sleep is used to introduce pause on execution, generally.
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1) When there is a clustered index on the table and the column to be queried, both the MAX() operator and the query SELECT TOP 1 will have almost identical performance. 2) When there is no clustered index on the table and the column to be queried, the MAX() operator offers the better performance.
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The solution One, it could be security. You need to make sure that the account under which your application is running has read/write access to the queue (or as high a permission level as you need). Second, make sure that if the queue is transactional, you're using the correct transaction mode for it.
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In general, DBCC CHECKDB should be executed while the database is ONLINE, but it is recommended that there is minimal activity on the SQL Server during this operation. It does not acquire table locks by default. Instead, it acquires schema locks that prevent metadata changes, but allow data changes.
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The main difference between deadlock prevention and deadlock avoidance is that the deadlock prevention ensures that at least one of the necessary conditions to cause a deadlock will never occur, while deadlock avoidance ensures that the system will not enter an unsafe state.
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Difference between WHERE and HAVING clause in SQL? The main difference between WHERE and HAVING clause comes when used together with GROUP BY clause, In that case WHERE is used to filter rows before grouping and HAVING is used to exclude records after grouping.
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The two types are exclusive and shared locks. Exclusive locks can be active or retained; shared locks can only be active (see Active and retained states for locks ). Note that there are no delete locks in RLS mode.
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The major difference is to wait to release the lock or monitor while sleep doesn't release any lock or monitor while waiting. Wait is used for inter-thread communication while sleep is used to introduce pause on execution.
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In databases and transaction processing, two-phase locking (2PL) is a concurrency control method that guarantees serializability. ... The protocol utilizes locks, applied by a transaction to data, which may block (interpreted as signals to stop) other transactions from accessing the same data during the transaction's life.
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An exclusive or write lock gives a process exclusive access for writing to the specified part of the file. ... A shared or read lock prohibits any other process from requesting a write lock on the specified part of the file. However, other processes can request read locks.
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Differences between the SQL Server DELETE and TRUNCATE Commands. Truncate reseeds identity values, whereas delete doesn't. Truncate removes all records and doesn't fire triggers. Truncate is faster compared to delete as it makes less use of the transaction log.
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No, UPDATE Statistics with Full Scan does not cause blocking. It is an online operation i.e. table will be available to read while statistics are updated.
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As we can see the difference between Nolock and With (Nolock) is that, the Nolock reads that data, which has not committed and can be rolled back. Thus, we can say that Nolock reads “Dirty Data” when applied with only Select statement in SQL Server Database.
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A deadlock is when two (or more) threads are blocking each other. Usually this has something to do with threads trying to acquire shared resources. ... Race conditions occur when two threads interact in a negatve (buggy) way depending on the exact order that their different instructions are executed.
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When i restarted the SQL Server, msdb got stuck in (recovery pending) mode. Any idea why? Check the permissions on the path and validate that the path is correct (file names included). Also make sure the files have been copied to the same path location specified in the query results you are getting.