What is a table-level lock?

Table-level locking systems always lock entire tables. For example, UPDATES that cannot use an index lock the entire table. Row-level locking systems can lock entire tables if a high number of single-row locks would be less efficient than a single table-level lock.

What is lock table in DB2?

The LOCK TABLE statement prevents concurrent application processes from using or changing a table. The lock is released when the unit of work issuing the LOCK TABLE statement either commits or terminates.

What are the different levels of lock granularity?

Each MySQL storage engine supports different levels of granularity for their locks. MySQL has three lock levels: row-level locking, page-level locking and table-level locking.

What are the various types of locks in DB2?

DB2 supports locking at four levels, or granularities: table space-, table-, page-, and row-level locking. DB2 also provides LOB locking for large objects (BLOBs, CLOBs, and DBCLOBs). Locks can be taken at any level in the locking hierarchy without taking a lock at the lower level.

What is table level locking and row level locking What is optimistic locking and pessimistic locking?

In SQL Server, the Repeatable Read isolation level is implemented using locking. If you read a row, you obtain a shared lock on that row, causing other transactions attempting to update the row to block until you commit or roll back your transaction. This behavior is very similar to pessimistic locking.

What is locking plane internal locking and table level locking?

Fast when used on a large part of the table because only a single lock is involved. Fast if you often do GROUP BY operations on a large part of the data or must scan the entire table frequently.

What are the different modes of lock?

At the table level, there are five different types of locks:

Exclusive (X)
Shared (S)
Intent exclusive (IX)
Intent shared (IS)
Shared with intent exclusive (SIX)

How is isolation level defined in Db2?

In Db2 you can specify the following four isolation levels:

cursor stability (CS),
repeatable read (RR),
read stability (RS), and.
uncommitted read (UR).

How many levels of locking are available?

Levels of Locks: Oracle provides the following three levels of Locking.

Why lock granularity is required?

Here, space refers to data structure in DBMS for each lock and time refers to handling of lock request and release. If a transaction typically accesses many records of the same file it is better to have block or file granularity so that the transaction will consider all those records as one data item.

What is the difference between optimistic and pessimistic lock?

Optimistic locking is when you check if the record was updated by someone else before you commit the transaction. Pessimistic locking is when you take an exclusive lock so that no one else can start modifying the record.