What factors are important when applying pessimistic locks in database systems?

Pessimistic locks in databases are used to prevent conflicts during concurrent data access. Important factors when using them:

• Transaction isolation level: Pessimistic locks are often associated with high isolation levels (e.g., Serializable), which can reduce performance.
• Lock duration: The longer a lock is held, the higher the likelihood of deadlocks and delays.
• Volume of locked data: Locking a large number of rows or tables can lead to decreased parallelism.
• Conflict frequency: If conflicts are rare, pessimistic locks may be excessive, and optimistic locking might be better.
• Type of lock: There are shared locks (read) and exclusive locks (write); choosing the appropriate type is important.

Proper application of pessimistic locks requires balancing data integrity and system performance.