What happens if you have a read lock before a write lock?
True. If you have the write lock before the read lock, the write lock will block other transactions to read or write the same table. If you have the read lock before the write lock, the read lock will block the write transactions until the reading transaction finishes. Sorry, I don’t understand this statement.
Can a row / table have a write lock at the same time?
(Even if the thread trying to write data doesn’t require a write lock.) A row/table cannot have a read and a write lock at the same time. When a row/table has a write lock, it cannot be read by another thread if they have a read lock implemented in them but can be read by other threads if no read lock is implemented (i.e simple Select query)
Can a thread have multiple read locks at the same time?
Multiple read locks can be acquired by multiple threads at the same time. True. Multiple read locks can exist at the same time. When a thread has a read lock on a row/table, no thread can update/insert/delete data from that table. (Even if the thread trying to write data doesn’t require a write lock.) True.
What are the symptoms of a bad door lock relay?
Usually a bad or failing door lock relay will produce a few symptoms that can alert the driver of a potential problem that should be serviced. One of the first symptoms of a possible problem with the door lock relay are door locks that function intermittently.
True. If you have the write lock before the read lock, the write lock will block other transactions to read or write the same table. If you have the read lock before the write lock, the read lock will block the write transactions until the reading transaction finishes. Sorry, I don’t understand this statement.
When to use nolock and readuncommitted lock hints?
The NOLOCK and READUNCOMMITTED lock hints are not allowed for target tables of INSERT, UPDATE, DELETE or MERGE statements. Schema Change Blocking with NOLOCK Since a NOLOCK hint needs to get a Sch-S (schema stability) lock, a SELECT using NOLOCK could still be blocked if a table is being altered and not committed. Here is an example.
(Even if the thread trying to write data doesn’t require a write lock.) A row/table cannot have a read and a write lock at the same time. When a row/table has a write lock, it cannot be read by another thread if they have a read lock implemented in them but can be read by other threads if no read lock is implemented (i.e simple Select query)
Multiple read locks can be acquired by multiple threads at the same time. True. Multiple read locks can exist at the same time. When a thread has a read lock on a row/table, no thread can update/insert/delete data from that table. (Even if the thread trying to write data doesn’t require a write lock.) True.