#Deadlock handling in dbms with example how to

It uses the intention lock modes to ensure serializability. Shared & Intention-Exclusive (SIX): In this lock, the node is locked in shared mode, and some node is locked in exclusive mode by the same transaction.Ĭompatibility Matrix with Intention Lock Modes: The below table describes the compatibility matrix for these lock modes: Intention-Exclusive (IX): It contains explicit locking at a lower level with exclusive or shared locks. Intention-shared (IS): It contains explicit locking at a lower level of the tree but only with shared locks. There are three additional lock modes with multiple granularity: Intention Mode Lock The levels below are file, record, and fields.

In this example, the highest level shows the entire database.

Hence, the levels of the tree starting from the top level are as follows:.

No records represent in more than one file. The file has exactly those records that are its child nodes.

Finally, each file contains child nodes known as records.

No file can be present in more than one area. The area consists of children nodes which are known as files.The higher level database consists of exactly these areas. The second level represents a node of type area.The first level or higher level shows the entire database.This type of hierarchy can be graphically represented as a tree.įor example: Consider a tree which has four levels of nodes. It makes easy to decide either to lock a data item or to unlock a data item.

#Deadlock handling in dbms with example how to

It maintains the track of what to lock and how to lock.

The Multiple Granularity protocol enhances concurrency and reduces lock overhead.

It can be defined as hierarchically breaking up the database into blocks which can be locked.Granularity: It is the size of data item allowed to lock. Let's start by understanding the meaning of granularity.