transaction and concurrency control

in data blocks: Each lock only affects one row of data blocks. Conflicting write process:1 A update operation2. Obtain the SCN and read the target data block.3. Record row lock Information4. Modify and write the redo log Cache5. Write rollback segments6. Update B7. Obtain the SCN and read data blocks.8. locks are found. If read committed is used to continue after execution is complete; if it is SERIALIZABLE, an error is returned.9 A commit A transaction10 if B READ COMMITTED, continue to execut

. 2. Multi-process concurrency control of LinuxRecently small a needs to produce the 2015 full-year KPI Data report, now small A has written the production script, production script can only produce a specified day of KPI data, assuming that a production script to run 5 minutes, then:* If the loop sequence is executed, then it takes time: 5 * 365 = 1825 minutes, approximately equal to 6 days* If it is put i

MySQL transaction isolation level solves concurrency issues, mysql transactions MySQL transaction isolation level 1. Dirty reading: the method of money fraud. Two windows or threads call the database transfer table respectively, but the table is not submitted after the transfer. After the other party sees the account, it rollback and the actual money is not t

Mysql transactions and multi-Version Concurrency control I. mysql transactions ?? A transaction is an atomic SQL query, or an independent unit of work. If the database engine can successfully execute all the statements in this group, execute the statements in this group. If one of the statements cannot be executed, none of the statements will be executed. That is

First Out)Named pipelines are also called FIFO. In terms of semantics, FIFO is actually similar to anonymous pipelines, but it is worth noting that: In a file system, FIFO has a name and exists in the form of a device-specific file; Any process can share data through FIFO; Unless there are read and write processes at both ends of the FIFO, the data flow of the FIFO will be blocked; Anonymous pipelines are automatically created by shell and exist in the kernel, whil

successfullyTransaction concurrency without transaction isolationDirty read: Transaction a reads data that is not committed by transaction B, and if transaction B fails to roll back at this point, then transaction A is reading di

transaction scope. There can be different implementations, but what they have in common is the isolation between unrelated transactions before the outermost transaction is ended, which means that nested transactions do not have to be persisted in updating the data into the database.Iv. concurrency controlGeneralized concurre