Updating a row in sql server 10p sex chat mobile
While objects are locked, SQL Server will prevent other transactions from making any change of data stored in objects affected by the imposed lock.Once the lock is released by committing the changes or by rolling back changes to initial state, other transactions will be allowed to make required data changes.This is an important lock type from the performance aspect as the SQL Server database engine will inspect intent locks only at the table level to check if it is possible for transaction to acquire a lock in a safe manner in that table, and therefore intent lock eliminates need to inspect each row/page lock in a table to make sure that transaction can acquire lock on entire table There are three regular intent locks and three so-called conversion locks: Intent exclusive (IX) – when an intent exclusive lock (IX) is acquired it indicates to SQL Server that the transaction has the intention to modify some of lower hierarchy resources by acquiring exclusive (X) locks individually on those lower hierarchy resources Intent shared (IS) – when an intent shared lock (IS) is acquired it indicates to SQL Server that the transaction has the intention to read some lower hierarchy resources by acquiring shared locks (S) individually on those resources lower in the hierarchy Intent update (IU) – when an intent shared lock (IS) is acquired it indicates to SQL Server that the transaction has the intention to read some of lower hierarchy resources by acquiring shared locks (S) individually on those resources lower in the hierarchy.The intent update lock (IU) can be acquired only at the page level and as soon as the update operation takes place, it converts to the intent exclusive lock (IX) Shared with intent exclusive (SIX) – when acquired, this lock indicates that the transaction intends to read all resources at a lower hierarchy and thus acquire the shared lock on all resources that are lower in hierarchy, and in turn, to modify part of those, but not all.An exclusive lock can be imposed to a page or row only if there is no other shared or exclusive lock imposed already on the target.This practically means that only one exclusive lock can be imposed to a page or row, and once imposed no other lock can be imposed on locked resources Shared lock (S) – this lock type, when imposed, will reserve a page or row to be available only for reading, which means that any other transaction will be prevented to modify the locked record as long as the lock is active.Once the transaction that holds the update lock is ready to change the data, the update lock (U) will be transformed to an exclusive lock (X).
The exclusive lock will be imposed by the transaction when it wants to modify the page or row data, which is in the case of DML statements DELETE, INSERT and UPDATE.
In practice, when a transaction wants to acquire a lock on the row, it will acquire an intent lock on a table, which is a higher hierarchy object.
By acquiring the intent lock, the transaction will not allow other transactions to acquire the exclusive lock on that table (otherwise, exclusive lock imposed by some other transaction would cancel the row lock).
In doing so, it will acquire an intent exclusive (IX) lock on those lower hierarchy resources that should be modified.
In practice, this means that once the transaction acquires a SIX lock on the table, it will acquire intent exclusive lock (IX) on the modified pages and exclusive lock (X) on the modified rows.