5 Questions
Explain the concept of lock-based protocols in concurrency control.
Lock-based protocols are a mechanism to control concurrent access to a data item. Data items can be locked in exclusive (X) mode, where the data item can be both read and written, or shared (S) mode, where the data item can only be read. Lock requests are made to the concurrency-control manager, and a transaction can proceed only after the request is granted.
How does a transaction proceed in lock-based protocols if a lock cannot be granted?
If a lock cannot be granted, the requesting transaction is made to wait until all incompatible locks held by other transactions have been released.
What is the role of the concurrency-control manager in lock-based protocols?
The concurrency-control manager is responsible for handling lock requests. Transactions can proceed only after their lock requests are granted by the concurrency-control manager.
What are the different modes in which data items can be locked in lock-based protocols?
Data items can be locked in exclusive (X) mode, where the data item can be both read and written, or shared (S) mode, where the data item can only be read.
What is a lock-compatibility matrix in the context of lock-based protocols?
A lock-compatibility matrix determines if a transaction may be granted a lock on an item based on whether the requested lock is compatible with locks already held on the item by other transactions. Any number of transactions can hold shared locks on an item, but if any transaction holds an exclusive lock on the item, no other transaction may hold any lock on the item.
Test your knowledge of concurrency control in database systems with this quiz. Explore topics such as lock-based protocols, timestamp-based protocols, validation-based protocols, multiple granularity, multiversion schemes, deadlock handling, and concurrency in index structures.
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