Moparscape Servers

for transaction processing power of additional requirements on the database server software. Transactions are generated at the client and sent to the server for processing. Very often, transactions affecting two or more tables with data that may reside on different machines. When the system crashes, software, database server must be able to return transactions that are underway and roll forward those transactions that were committed before the crash, but not reflected in a recent database backup.

This process has one or more operations that are performed together to complete a simple change of address zadatka.Poštansku transakcija.Nešto complex transactions, the banking transactions that balance one account and credits another.

The transaction is considered successful, all operations must be carried out. If any work of the transaction can be completed, operations that have the effect must be reversed, a process that is called to commit and rollback. While executing the steps of the transaction, the system keeps a diary of work, including before and after pictures of data. When the transaction is successfully completed, the system commits all changes permanently. If the transaction is successfully completed, the system uses the log back into the database to the state before the execution. This function is mandatory for transaction processing systems to the database in a consistent state between transactions.

to commit, and restore facilities are focused on recovery from data errors or software failures. Protective measures for hardware failures, such as power outages or hardware failure, should also be taken into account. Some protections are typical uninterruptible power supplies and disk mirroring, which copies the data to separate disks so that if one drive fails the other can be accessed.

In distributed processing, transactions have the following characteristics:

Consistency:. Systems and resources to go from one state to another stable

Isolation: the effect of the transaction is not clear on other tasks while the transaction is committed. However, all information that the transaction is in progress to be locked to prevent other transactions from changing it.

Endurance:. The effects of the transaction are permanent and not affected by system failure

two-phase commit:

two-phase commit ensures data consistency and completeness of this transaction processing is used when more than one table.

Lock Scheme

This processing applications also requires the use of locking schemes to ensure that the database user access to protected while in use. When a transaction locks the record, that record can not be updated until the lock is released.