devialet phantom

Spring Propagation PropertiesPropagation_required:The method must be running in a transaction. If a transaction is running, the method will run in this transaction. Otherwise, a new transaction is started.Isolation level for spring transactions1. Isolation_default: This is a platfromtransactionmanager default isolation level, using the default transaction isolation level of the database.The other four correspond to the isolation level of JDBC2. Isolation_read_uncommitted: This is the lowest isol

Dirty Read dirty reads: This event occurs when a transaction reads data that has not yet been committed. For example: Transaction 1 modifies a row of data, and Transaction 2 reads the modified row before Transaction 1 has committed the modification operation. If transaction 1 rolls back the modification operation, the data read by transaction 2 can be seen as never existed.Non-repeatable Read non-repeatable reads: This event occurs when a transaction reads the same row of data two times, but eac

update, dirty read, non-repeated read, and phantom read. The above example is only one of the concurrency problems. (1) lost update) When two or more transactions select the same data and update the data based on the originally selected value, the update will be lost. Every transaction does not know the existence of other transactions. The last update will overwrite the updates made by other firms, which will lead to data loss. The

. The first application may then request to roll back the modified data, resulting in data corruption in the second transaction, that is, the so-called "dirty ". Unrepeatable read: A transaction reads the same row of data twice, but the data read these two times is different. If a transaction can modify or delete the data before committing the data, it cannot be re-viewed. Phantom read: A transaction executes two queries and finds that the second quer

The c ++ implementation of any level magic is odd level magic, dual-even magic, and single-even magic ., Magic single doll Magic is divided into three categories. Odd Magic Square (odd number), double-even magic square (can be divided by four, such as 8, 12, 16 ......) , Single-doll Magic Square (4 m + 2 forms, such as 6, 10 ......), The constructor algorithms are different. In the following program, the Construction Algorithm of the odd magic square is the Merzirac method. The Construction Algo

when reading data concurrently. However, theoretically, this will lead to another tricky problem: Phantom Read ). In short, phantom read refers to when a user reads data in a certain range, another transaction inserts a new row in this range. When the user reads data in this range, there will be a new Phantom line. The InnoDB and Falcon storage engines solve thi

case, non-repeated read occurs. (A transaction rereads data it has previusy read and finds that another committed transaction has modified or deeted the data .) Phantom read: The same query is performed multiple times in the same transaction. Because of the insert operations performed by other commit firms, different result sets are returned each time. In this case, a phantom read occurs. (A transaction r

We can include the entire package in SSIS in a transaction. But what if a table needs to be locked during package execution? The built-in transaction processing of SSIS can solve this problem. Before that, familiarize yourself with the concept of transactions in SQL Server. Transactions Transactions in SQL Server are a single unit of work. If a transaction succeeds, all data modifications made in the transaction will be committed and become a permanent component of the database. If the transacti

online. Use phantom resources to complete configurationThe phantom resource is used to report the actual status of a Service Group composed of only permanent resources. A Service Group is only online when all non-permanent resources are online. Therefore, if a service group only has permanent resources, VCs considers the group to be offline, even if the permanent resources are running properly, by adding a

determines the degree to which a transaction can be affected by other parallel transactions1. Why is there a transaction isolation level and a problem that can be resolved (why)?In a multi-user system, the concept of transaction isolation mechanism is introduced in order to ensure the consistency and integrality of data, avoid dirty reading, non-repetition reading and phantom reading, etc.2. Dirty reading, non-repeatable reading,

commits the modification, while the other commits the modification. This will cause the first write operation to fail.5, Phantom Reading (Phantom reads)Transactions are queried two times during the operation, and the results of the second query include the first check Four isolation levels: ReadCommitted: Assuming that a transaction places a shared lock on the data being read, then data cannot be overwritt

results.Repeatable Read (can be reread)This is the default transaction isolation level for MySQL, which ensures that multiple instances of the same transaction will see the same rows of data while concurrently reading the data. In theory, however, this can lead to another tricky problem: Phantom Reading (Phantom read). To put it simply, Phantom reads when a user

method.SET autocommit=0, a clear command is required to commit or rollback.5. Problems caused by transaction concurrencyDirty Reads (Dirty read) refers to a transaction (a) that reads a different transaction (B) uncommitted change data and operates on the basis of the data being read. If the B transaction happens to be rolled back, then the data read by a transaction is not recognized at all.Non-repeatable read (unrepeatable read) refers to a transaction that reads the change data that the B tr