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Computer Interview Questions Answers

Oracle Interview Questions Answers

Question - 201 : - Where should the tuning effort be directed?

Answer - 201 : - Consider the following areas for tuning. The order in which steps are listed needs to be maintained to prevent tuning side effects. For example, it is no good increasing the buffer cache if you can reduce I/O by rewriting a SQL statement. Database Design (if it's not too late): Poor system performance usually results from a poor database design. One should generally normalize to the 3NF. Selective denormalization can provide valuable performance improvements. When designing, always keep the "data access path" in mind. Also look at proper data partitioning, data replication, aggregation tables for decision support systems, etc. Application Tuning: Experience showed that approximately 80% of all Oracle system performance problems are resolved by coding optimal SQL. Also consider proper scheduling of batch tasks after peak working hours. Memory Tuning: Properly size your database buffers (shared pool, buffer cache, log buffer, etc) by looking at your buffer hit ratios. Pin large objects into memory to prevent frequent reloads. Disk I/O Tuning: Database files needs to be properly sized and placed to provide maximum disk subsystem throughput. Also look for frequent disk sorts, full table scans, missing indexes, row chaining, data fragmentation, etc Eliminate Database Contention: Study database locks, latches and wait events carefully and eliminate where possible. Tune the Operating System: Monitor and tune operating system CPU, I/O and memory utilization. For more information, read the related Oracle FAQ dealing with your specific operating system.

Question - 202 : - Explain about stacked canvas views?

Answer - 202 : - Stacked canvas view is displayed in a window on top of, or "stacked" on the content canvas view assigned to that same window. Stacked canvas views obscure some part of the underlying content canvas view, and or often shown and hidden programmatically.

Question - 203 : - Which of the two views should objects according to possession?

Answer - 203 : - view by structure.

Question - 204 : - Can a View based on another View ?

Answer - 204 : - Yes.

Question - 205 : - What is an Oracle index?

Answer - 205 : - An index is an optional structure associated with a table to have direct access to rows, which can be created to increase the performance of data retrieval. Index can be created on one or more columns of a table.

Question - 206 : - What are the different default triggers created when Master Deletes Property is set to Non-isolated?

Answer - 206 : - Master Deletes Property Resulting Triggers ---------------------------------------------------- Non-Isolated(the default) On-Check-Delete-Master On-Clear-Details On-Populate-Details

Question - 207 : - How does one do on-line database backups?

Answer - 207 : - Each tablespace that needs to be backed-up must be switched into backup mode before copying the files out to secondary storage (tapes). Look at this simple example. ALTER TABLESPACE xyz BEGIN BACKUP; ! cp xyfFile1 /backupDir/ ALTER TABLESPACE xyz END BACKUP; It is better to backup tablespace for tablespace than to put all tablespaces in backup mode. Backing them up separately incurs less overhead. When done, remember to backup your control files. Look at this example: ALTER SYSTEM SWITCH LOGFILE; -- Force log switch to update control file headers ALTER DATABASE BACKUP CONTROLFILE TO '/backupDir/control.dbf'; NOTE: Do not run on-line backups during peak processing periods. Oracle will write complete database blocks instead of the normal deltas to redo log files while in backup mode. This will lead to excessive database archiving and even database freezes.

Question - 208 : - What is difference between open_form and call_form?

Answer - 208 : - when one form invokes another form by executing open_form the first form remains displayed, and operators can navigate between the forms as desired. when one form invokes another form by executing call_form, the called form is modal with respect to the calling form. That is, any windows that belong to the calling form are disabled, and operators cannot navigate to them until they first exit the called form.

Question - 209 : - What are modal windows?

Answer - 209 : - Modal windows are usually used as dialogs, and have restricted functionality compared to modelless windows. On some platforms for example operators cannot resize, scroll or iconify a modal window.

Question - 210 : - Atleast how many set of data must a data model have before a data model can be base on it?

Answer - 210 : - Four

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