Explain what is meant by pessimistic locking in the context of data access management.

Pessimistic locking is a data access management strategy where a lock is immediately established when reading or modifying data, preventing other transactions from accessing the data simultaneously. This guarantees that the data will not be altered by other processes until the current transaction is completed, thus avoiding conflicts and ensuring integrity.

For example, in a database, during pessimistic locking, a record is locked during editing, and other transactions attempting to access this record will wait for the lock to be released.

This differs from optimistic locking, where conflicts are only checked at the time of saving changes.