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Redo log. In the Oracle RDBMS environment, redo logs comprise files in a proprietary format which log a history of all changes made to the database. Each redo log file consists of redo records. A redo record, also called a redo entry, holds a group of change vectors, each of which describes or represents a change made to a single block in the ...
Write-ahead logging. In computer science, write-ahead logging (WAL) is a family of techniques for providing atomicity and durability (two of the ACID properties) in database systems. [1] A write ahead log is an append-only auxiliary disk-resident structure used for crash and transaction recovery. The changes are first recorded in the log, which ...
Once the archived redo logs have arrived on the standby host, other processes - such as an ARCH (archiver process), an MRP (Managed Recovery Process [10]), and/or an LSP (Logical Standby Process) - may set about applying the log contents to the standby database. The use of standby redo logs can speed up the application of changes to a standby ...
We create log records of the form (Sequence Number, Transaction ID, Page ID, Redo, Undo, Previous Sequence Number). The Redo and Undo fields keep information about the changes this log record saves and how to undo them. The Previous Sequence Number is a reference to the previous log record that was created for this transaction.
Database activity monitoring. Database activity monitoring (DAM, a.k.a. Enterprise database auditing and Real-time protection[1]) is a database security technology for monitoring and analyzing database activity. DAM may combine data from network-based monitoring and native audit information to provide a comprehensive picture of database activity.
Transaction log. In the field of databases in computer science, a transaction log (also transaction journal, database log, binary log or audit trail) is a history of actions executed by a database management system used to guarantee ACID properties over crashes or hardware failures. Physically, a log is a file listing changes to the database ...
The database consists of a collection of data files, control files, and redo logs located on disk. The instance comprises the collection of Oracle-related memory and background processes that run on a computer system. In an Oracle RAC environment, 2 or more instances concurrently access a single database.
Brad Wolverton is a senior writer and Sandhya Kambhampati is a database reporter at The Chronicle of Higher Education. Design and art direction by Hilary Fung and Alissa Scheller, visual editors for HuffPost. Reporting contributions from Nicky Forster, data fellow for HuffPost, and Isaac Stein, reporting intern for The Chronicle.