Oracle Interview Questions and Answers
Question - 101 : - What is a SNAPSHOT ?
Answer - 101 : - Snapshots are read-only copies of a master table located on a remote node which is periodically refreshed to reflect changes made to the master table.
Question - 102 : - What is the mechanism provided by ORACLE for table replication ?
Answer - 102 : - Snapshots and SNAPSHOT LOGs
Question - 103 : - What is snapshots?
Answer - 103 : - Snapshot is an object used to dynamically replicate data between distribute database at specified time intervals. In ver 7.0 they are read only.
Question - 104 : - What are the various type of snapshots?
Answer - 104 : - Simple and Complex.
Question - 105 : - Describe two phases of Two-phase commit ?
Answer - 105 : - 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.
Question - 106 : - What is snapshot log ?
Answer - 106 : - 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.
Question - 107 : - What are the benefits of distributed options in databases?
Answer - 107 : - 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.
Question - 108 : - What are the options available to refresh snapshots ?
Answer - 108 : - 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.
Question - 109 : - What is a SNAPSHOT LOG ?
Answer - 109 : - 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.
Question - 110 : - What is Distributed database ?
Answer - 110 : - 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.