Tree Based Protocol MCQ Quiz - Objective Question with Answer for Tree Based Protocol - Download Free PDF

The correct answer is option 1: Intention lock modes

Key Points

• Intention lock modes are used in hierarchical databases or B-trees to signal that a transaction intends to lock a lower-level node.
• They are not actual locks on the data itself, but a way to coordinate locking at multiple levels in a structure.
• Types of intention locks include:
  • IS (Intention Shared): Intention to acquire shared locks at lower levels.
  • IX (Intention Exclusive): Intention to acquire exclusive locks at lower levels.
  • SIX (Shared and Intention Exclusive): Shared lock on current node, intention to get exclusive locks on children.
• If a node is locked with an intention lock, it means **explicit locking** is happening at lower levels with **S (Shared)** or **X (Exclusive)** locks.

Additional Information

• IX mode and IS mode are individual types of intention lock modes, but the question asks for the broader mechanism.
• Intention lock modes as a whole describe the strategy of locking a node while intending to lock children at a lower level.

Hence, the correct answer is: option 1: Intention lock modes

The correct answer is: option 4: Six

Concept:

In **multiple-granularity locking**, a transaction can request locks at different levels of a hierarchy (e.g., database, table, page, record), and **six types of lock modes** are defined to support both shared and exclusive access while maintaining concurrency control.

The six lock modes are:

1. IS (Intent Shared) – Indicates intention to acquire shared locks at a lower level.
2. IX (Intent Exclusive) – Indicates intention to acquire exclusive locks at a lower level.
3. S (Shared) – Allows shared access to a data item.
4. SIX (Shared Intent Exclusive) – A combination of S and IX. Shared lock on current level and intent exclusive on lower levels.
5. X (Exclusive) – Allows read and write access to a data item.
6. NULL – No lock held (may be considered in lock compatibility matrices).

Explanation of options:

• Option 1 – Two: ❌ Only covers S and X, not sufficient for multigranularity.
• Option 2 – Five: ❌ Missing one of the standard modes.
• Option 3 – Three: ❌ Too few; excludes intent modes.
• Option 4 – Six: ✅ Correct. Standard multigranularity locking defines six modes.

Hence, the correct answer is: option 4: Six

The correct answer is option 1: Intention lock modes

Key Points

• Intention lock modes are used in hierarchical databases or B-trees to signal that a transaction intends to lock a lower-level node.
• They are not actual locks on the data itself, but a way to coordinate locking at multiple levels in a structure.
• Types of intention locks include:
  • IS (Intention Shared): Intention to acquire shared locks at lower levels.
  • IX (Intention Exclusive): Intention to acquire exclusive locks at lower levels.
  • SIX (Shared and Intention Exclusive): Shared lock on current node, intention to get exclusive locks on children.
• If a node is locked with an intention lock, it means **explicit locking** is happening at lower levels with **S (Shared)** or **X (Exclusive)** locks.

Additional Information

• IX mode and IS mode are individual types of intention lock modes, but the question asks for the broader mechanism.
• Intention lock modes as a whole describe the strategy of locking a node while intending to lock children at a lower level.

Hence, the correct answer is: option 1: Intention lock modes

The correct answer is: option 4: Six

Concept:

In **multiple-granularity locking**, a transaction can request locks at different levels of a hierarchy (e.g., database, table, page, record), and **six types of lock modes** are defined to support both shared and exclusive access while maintaining concurrency control.

The six lock modes are:

1. IS (Intent Shared) – Indicates intention to acquire shared locks at a lower level.
2. IX (Intent Exclusive) – Indicates intention to acquire exclusive locks at a lower level.
3. S (Shared) – Allows shared access to a data item.
4. SIX (Shared Intent Exclusive) – A combination of S and IX. Shared lock on current level and intent exclusive on lower levels.
5. X (Exclusive) – Allows read and write access to a data item.
6. NULL – No lock held (may be considered in lock compatibility matrices).

Explanation of options:

• Option 1 – Two: ❌ Only covers S and X, not sufficient for multigranularity.
• Option 2 – Five: ❌ Missing one of the standard modes.
• Option 3 – Three: ❌ Too few; excludes intent modes.
• Option 4 – Six: ✅ Correct. Standard multigranularity locking defines six modes.

Hence, the correct answer is: option 4: Six

In addition to S(shared) and X(exclusive) lock modes, there are three additional lock

modes with multiple granularity:

●   intention-shared(IS): indicates explicit locking at a lower level of the tree but only with shared locks.

●   intention-exclusive (IX): indicates explicit locking at a lower level with exclusive or shared locks .

●  shared and intention-exclusive (SIX): the subtree rooted by that node is locked explicitly in shared mode and explicit locking is being done at a lower level with exclusive-mode locks.

Intention locks allow a higher level node to be locked in S or X mode without having to check all descendent nodes.

The compatibility matrix for all lock modes is: