What is starvation Java?

Starvation describes a situation where a thread is unable to gain regular access to shared resources and is unable to make progress. This happens when shared resources are made unavailable for long periods by “greedy” threads.

What is deadlock Java?

Deadlock describes a situation where two or more threads are blocked forever, waiting for each other. A Java multithreaded program may suffer from the deadlock condition because the synchronized keyword causes the executing thread to block while waiting for the lock, or monitor, associated with the specified object.

How can we resolve deadlock?

A deadlock occurs when the first process locks the first resource at the same time as the second process locks the second resource. The deadlock can be resolved by cancelling and restarting the first process.

What causes a SQL deadlock?

A deadlock happens when two (or more) transactions block each other by holding locks on resources that each of the transactions also need. For example: Transaction 1 holds a lock on Table A. Most people will write that deadlocks cannot be avoided in a multi-user database.

How can we avoid deadlock in DBMS?

Deadlock avoidance mechanism is used to detect any deadlock situation in advance. A method like “wait for graph” is used for detecting the deadlock situation but this method is suitable only for the smaller database. For the larger database, deadlock prevention method can be used.

What is a deadlock victim?

By default, SQL Server chooses as the deadlock victim the transaction that is least expensive to rollback. In simple terms, a transaction that makes the fewest changes to the database is considered the least expensive. The process with the lowest deadlock priority will then be the one chosen as the deadlock victim.

What are the 4 conditions required for deadlocks to occur?

Four Necessary and Sufficient Conditions for Deadlock

mutual exclusion. The resources involved must be unshareable; otherwise, the processes would not be prevented from using the resource when necessary.
hold and wait or partial allocation.
no pre-emption.
resource waiting or circular wait.

How do I know if a deadlock is enabled?

You can check the status of the trace flag using the DBCC TRACESTATUS (1222, -1) command. You can see by the following results that the trace flag is enabled, and that it is enabled globally. You can turn off the trace flag any time by simply issuing the DBCC TRACEOFF (1222,-1) command.

How do I trace a deadlock in SQL Profiler?

To trace deadlock events, add the Deadlock graph event class to a trace. This event class populates the TextData data column in the trace with XML data about the process and objects that are involved in the deadlock. SQL Server Profiler can extract the XML document to a deadlock XML (.

How do I know if a trace flag is enabled?

Just get to the Server node on Object Explorer (SSMS) -> Right Click -> Reports -> Standard Reports -> “Server Dashboard”. Once you are here, you can expand the “Non-Default Configuration Options” and there are these Trace Flags that are enabled “Globally” on a given server.

How deadlock is detected in DBMS?

Wait-for-graph is one of the methods for detecting the deadlock situation. This method is suitable for smaller database. In this method a graph is drawn based on the transaction and their lock on the resource. If the graph created has a closed loop or a cycle, then there is a deadlock.

What is locking in DBMS?

A lock is a data variable which is associated with a data item. This lock signifies that operations that can be performed on the data item. Locks in DBMS help synchronize access to the database items by concurrent transactions. All lock requests are made to the concurrency-control manager.

What is starvation in DBMS?

Starvation or Livelock is the situation when a transaction has to wait for a indefinite period of time to acquire a lock. Reasons of Starvation – If waiting scheme for locked items is unfair. ( priority queue )

What is two phase locking in DBMS?

In databases and transaction processing, two-phase locking (2PL) is a concurrency control method that guarantees serializability. The protocol utilizes locks, applied by a transaction to data, which may block (interpreted as signals to stop) other transactions from accessing the same data during the transaction’s life.

Is strict 2PL deadlock free?

arrow_back Strict and Conservative 2PL. Conservative 2PL is deadlock free,but Strict 2PL can have deadlock.

Why is strict 2PL popular?

Strict 2PL is popular for many reasons. One reason is that it ensures only ‘safe’ interleaving of transactions so that transactions are recoverable, avoid cascading aborts, etc. Another reason is that strict 2PL is very simple and easy to implement. Transaction T1 reads objects X and Y and then writes object X.

What is the difference b W strict 2PL and rigorous 2PL give example?

Rigorous two-phase locking is even stricter: here all locks are held till commit/abort. In this protocol transactions can be serialized in the order in which they commit. Same as Strict 2PL but Hold all locks until the transaction has already successfully committed or aborted.

What is the problem of distributed deadlock detection?

Deadlocks is a fundamental problem in distributed systems. A process may request resources in any order, which may not be known a priori and a process can request resource while holding others. If the sequence of the allocations of resources to the processes is not controlled, deadlocks can occur.

What are the two methods for dealing deadlock problem?

Methods for Handling Deadlocks

Deadlock Detection. Deadlock can be detected by the resource scheduler as it keeps track of all the resources that are allocated to different processes.
Deadlock Prevention. It is important to prevent a deadlock before it can occur.
Deadlock Avoidance.
Ostrich Algorithm.