Example: In a transfer, money is transferred from one account to another. This means that money is debited from one account and credited to another account. Roughly speaking, these are two changes, because the amount of money is deducted from the first account and this amount is added to the second account. These two changes are directly linked and dependent on each other. However, if the debit of the amount of money is successful but the credit fails, then the money has been destroyed. In the opposite case, if the debit fails but the credit is successful, then the money has been increased. In both cases, the consistency of the database is disrupted because it is not possible to trace where the corresponding amount of money went or where it came from.
These two changes must necessarily be viewed as a unit and combined in a transaction. In Oracle, transactions are started with the login and the first change to data. If afghanistan telegram screening further changes follow, these are included in the currently running transaction. This transaction can be committed with the COMMIT command if the change is successful, and reversed with the ROLLBACK command if individual changes are unsuccessful. After the transaction has been committed or rolled back, a new transaction automatically starts when data is changed again.
The System Global Area (SGA) contains the storage structures of the Oracle instance, which store table data, metadata or system information of the database, among other things. The storage structures include, for example, the database buffer cache, the redo log buffer, the shared pool, the large pool, the Java pool and other storage areas not explained in detail here.