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Oracle Interview Questions And Answers
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- to collect statisties about object used by the optimizer and store them in the data dictionary. - to delete statistics about the object used by object from the data dictionary. - to validate the structure of the object. - to identify migrated and chained rows of the table or cluster. MANAGING DISTRIBUTED DATABASES. 62. How can we reduce the network traffic ? - Replictaion of data in distributed environment. - Using snapshots to replicate data. - Using remote procedure calls. 63. What is snapshots ? Snapshot is an object used to dynamically replicate data between distribute database at specified time intervals. In ver 7.0 they are read only. 64. What are the various type of snapshots ? Simple and Complex. 65. Differentiate simple and complex, snapshots ? - A simple snapshot is based on a query that does not contains GROUP BY clauses, CONNECT BY clauses, JOINs, sub-query or snashot of operations. - A complex snapshots contain atleast any one of the above. 66. What dynamic data replication ? Updating or Inserting records in remote database through database triggers. It may fail if remote database is having any problem. 67. How can you Enforce Refrencial Integrity in snapshots ? Time the references to occur when master tables are not in use. Peform the reference the manually immdiately locking the master tables. We can join tables in snopshots by creating a complex snapshots that will based on the master tables. 68. What are the options available to refresh snapshots ? COMPLETE - Tables are completly regenerated using the snapshot's 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. 69. what is snapshot log ? |