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In relational databases, the log trigger or history trigger is a mechanism for automatic recording of information about changes inserting or/and updating or/and deleting rows in a database table. It is a particular technique for change data capturing , and in data warehousing for dealing with slowly changing dimensions .
The technique transforms an application SQL statement from an innocent SQL call to a malicious call that can cause unauthorized access, deletion of data, or theft of information. [ 3 ] One way that DAM can prevent SQL injection is by monitoring the application activity, generating a baseline of “normal behavior”, and identifying an attack ...
This implies database logs are constructed in linked list form. Transaction ID number: A reference to the database transaction generating the log record. Type: Describes the type of database log record. Information about the actual changes that triggered the log record to be written.
Most database management systems do not document the internal format of their transaction logs, although some provide programmatic interfaces to their transaction logs (for example: Oracle, DB2, SQL/MP, SQL/MX and SQL Server 2008). Other challenges in using transaction logs for change data capture include:
SQL refers to Structured Query Language, a kind of language used to access, update and manipulate database. In SQL, ROLLBACK is a command that causes all data changes since the last START TRANSACTION or BEGIN to be discarded by the relational database management systems (RDBMS), so that the state of the data is "rolled back" to the way it was before those changes were made.
This includes transactions that completed after this transaction's start time, and optionally, transactions that are still active at validation time. Commit/Rollback: If there is no conflict, make all changes take effect. If there is a conflict, resolve it, typically by aborting the transaction, although other resolution schemes are possible.
Oracle uses that current group to write the redo log entries. When the group is full, a log switch occurs, making another group the current one. Each log switch causes checkpoint, however, the converse is not true: a checkpoint does not cause a redo log switch. One can also manually cause a redo-log switch using the ALTER SYSTEM SWITCH LOGFILE ...
In databases, and transaction processing (transaction management), snapshot isolation is a guarantee that all reads made in a transaction will see a consistent snapshot of the database (in practice it reads the last committed values that existed at the time it started), and the transaction itself will successfully commit only if no updates it has made conflict with any concurrent updates made ...