The dynamic performance views are special views that are continuously updated while a database is open and in use. Throughout its operation, Oracle Database maintains a set of virtual tables that record current database activity.These views are dynamic because they are continuously updated while a database is open and in use. The views are sometimes … Read more
A lock is a mechanism that prevents destructive interactions. Interactions are destructive when they incorrectly update data or incorrectly alter underlying data structures, between transactions accessing shared data. Locks play a crucial role in maintaining database concurrency and consistency. Summary of Locking Behavior The database maintains several different types of locks, depending on the operation … Read more
Problem:While patching 19.3 GRID_HOME with July2019 RU patch 19.4 I got this error: Solution:The problem was with the RU patch binaries, looks the files were not copied properly, extracting the binaries properly from the zip file has fixed the problem!Initially, copied the “extracted” RU binary files from another node, seems they were incomplete.
Instance recovery is the process of applying records in the online redo log to data files to reconstruct changes made after the most recent checkpoint. Instance recovery occurs automatically when an administrator attempts to open a database that was previously shut down inconsistently. Purpose of Instance Recovery Instance recovery ensures that the database is in … Read more
Typically, you manually start an instance, and then mount and open the database, making it available for users. You can use the SQL*Plus STARTUP command, Oracle Enterprise Manager (Enterprise Manager), or the SRVCTL utility to perform these steps. To start a database instance using Oracle Net, the following must be true: The listener creates a … Read more
The most crucial structure for recovery is the online redo log, which consists of two or more preallocated files that store changes to the database as they occur. The online redo log records changes to the data files. Use of the Online Redo Log The database maintains online redo log files to protect against data … Read more
A deadlock is a situation in which two or more users are waiting for data locked by each other. Deadlocks prevent some transactions from continuing to work. Oracle Database automatically detects deadlocks and resolves them by rolling back one statement involved in the deadlock, releasing one set of the conflicting row locks. The database returns … Read more
The central set of read-only reference tables and views of each Oracle database is known collectively as the data dictionary. Overview of the Data Dictionary An important part of an Oracle database is its data dictionary, which is a read-only set of tables that provides administrative metadata about the database. A data dictionary contains information … Read more
Purpose: Use a constraint to define an integrity constraint—a rule that restricts the values in a database. The Oracle server uses constraints to prevent invalid data entry into tables. You can use constraints to do the following: • Enforce rules on the data in a table whenever a row is inserted, updated, or deleted from … Read more