What is the main limitation of Oracle databases?
Complexity. One of the biggest disadvantages of Oracle Database is its complexity. It is not preferable to use Oracle, especially when the users are not technically sound and lack the technical ability that is needed in order to work with the Oracle Database.
What is Flashback privilege in Oracle?
Oracle Flashback Table provides the DBA the ability to recover a table or set of tables to a specified point in time in the past very quickly, easily, and without taking any part of the database offline.
Does Oracle allow dirty reads?
Oracle Database doesn’t use dirty reads, nor does it even allow them. The basic goal of a READ UNCOMMITTED isolation level is to provide a standards-based definition that allows for nonblocking reads.
How does Flashback work in Oracle?
Use the FLASHBACK DATABASE command to rewind the database to a target time, SCN, or log sequence number. This command works by undoing changes made by Oracle Database to the data files that exist when you run the command. Flashback can fix logical failures, but not physical failures.
What is the limit of a database?
A Database Limits Limits exist on several levels in the database. There is usually a hard-coded limit in the database that cannot be exceeded. This value may be further restricted for any given operating system.
What is the main limitation of hierarchical database?
Discussion Forum
| Que. | What is the main limitation of Hierarchical Databases? |
|---|---|
| b. | Limited flexibility in accessing data |
| c. | Overhead associated with maintaining indexes |
| d. | The performance of the database is poor |
| Answer:Limited flexibility in accessing data |
What is the difference between rollback and flashback in Oracle?
The main difference is that flashback rolls back changes including the changes made by others in the whole table or database to any point of time in the past within the range of flashback setting.
How do you do a flashback query?
You perform a Flashback Query using a SELECT statement with an AS OF clause. You use a Flashback Query to retrieve data as it existed at some time in the past. The query explicitly references a past time using a timestamp or SCN. It returns committed data that was current at that point in time.
What is a phantom read in Oracle?
A phantom read is a special case of fuzzy reads. This happens when another session inserts or deletes rows that match the where clause of your query. So repeated queries can return different rows: Transaction 1. Transaction 2.
Does Flashback database need archive logs?
The requirements for enabling Flashback Database are: Your database must be running in ARCHIVELOG mode, because archived logs are used in the Flashback Database operation. You must have a flash recovery area enabled, because flashback logs can only be stored in the flash recovery area.
What are flashback features in Oracle Database?
With flashback features, you can: Perform queries that return metadata that shows a detailed history of changes to the database Roll back a transaction and its dependent transactions while the database remains online Oracle Flashback features use the Automatic Undo Management (AUM) system to obtain metadata and historical data for transactions.
What are the prerequisites for using Oracle Flashback Query?
Prerequisites. Oracle Flashback Query can only be used if the server is configured to use Automatic Undo Management, rather than traditional rollback segments. The maximum time period that can be flashbacked to is defined using the UNDO_RETENTION parameter in the init.ora file. Alternatively, this parameter can be set using the following command.
How to perform queries on past data in flashback Data Archive?
You can perform queries on past data in static data dictionary views, such as *_TABLES. As of Oracle Database 11 g Release 2 (11.2.0.4), you can enable optimization of data storage for history tables maintained by Flashback Data Archive by specifying OPTIMIZE DATA when creating or altering a Flashback Data Archive.
How do I enable flashback Data Archive in Oracle Total Recall?
For Flashback Data Archive (Oracle Total Recall) To allow a specific user to enable Flashback Data Archive on tables, using a specific Flashback Data Archive, grant the FLASHBACK ARCHIVE object privilege on that Flashback Data Archive to that user.