10 Apr, 2007
Database Interview Questions
- What are the various type of snapshots? - Simple and Complex.
- Describe two phases of Two-phase commit? - Prepare phase - The global coordinator (initiating node) ask a participants to prepare (to promise to commit or rollback the transaction, even if there is a failure) Commit - Phase - If all participants respond to the coordinator that they are prepared, the coordinator asks all nodes to commit the transaction, if all participants cannot prepare, the coordinator asks all nodes to roll back the transaction.
- What is snapshot log? - It is a table that maintains a record of modifications to the master table in a snapshot. It is stored in the same database as master table and is only available for simple snapshots. It should be created before creating snapshots.
- What are the benefits of distributed options in databases? - Database on other servers can be updated and those transactions can be grouped together with others in a logical unit. Database uses a two phase commit.
- What are the options available to refresh snapshots? - COMPLETE - Tables are completely regenerated using the snapshots query and the master tables every time the snapshot referenced. FAST - If simple snapshot used then a snapshot log can be used to send the changes to the snapshot tables. FORCE - Default value. If possible it performs a FAST refresh; Otherwise it will perform a complete refresh.
- What is a SNAPSHOT LOG? - A snapshot log is a table in the master database that is associated with the master table. ORACLE uses a snapshot log to track the rows that have been updated in the master table. Snapshot logs are used in updating the snapshots based on the master table.
- What is Distributed database? - A distributed database is a network of databases managed by multiple database servers that appears to a user as single logical database. The data of all databases in the distributed database can be simultaneously accessed and modified.
- How can we reduce the network traffic? - Replication of data in distributed environment. - Using snapshots to replicate data. - Using remote procedure calls.
- Differentiate simple and complex, snapshots? - A simple snapshot is based on a query thaat does not contains GROUP BY clauses, CONNECT BY clauses, JOINs, sub-query or snapshot of operations. - A complex snapshots contain at least any one of the above.
- What are the Built-ins used for sending Parameters to forms? - You can pass parameter values to a form when an application executes the call_form, New_form, Open_form or Run_product.
- Can you have more than one content canvas view attached with a window? - Yes. Each window you create must have at least one content canvas view assigned to it. You can also create a window that has manipulated content canvas view. At run time only one of the content canvas views assign to a window is displayed at a time.
