Oracle Interview Questions And Answers

33. What is Data Block ? ORACLE database's data is stored in data blocks. One data block corresponds to a specific number of bytes of physical database space on disk. 34. How to define Data Block size ? A data block size is specified for each ORACLE database when the database is created. A database users and allocated free database space in ORACLE datablocks. Block size is specified in INIT.ORA file and cann't be changed latter. 35. What is Row Chaining ? In Circumstances, all of the data for a row in a table may not be able to fit in the same data block. When this occurs , the data for the row is stored in a chain of data block (one or more) reserved for that segment. 36. What is an Extent ? An Extent is a specific number of contiguous data blocks, obtained in a single allocation, used to store a specific type of information. 37. What is a Segment ? A segment is a set of extents allocated for a certain logical structure. 38. What are the different type of Segments ? Data Segment, Index Segment, Rollback Segment and Temporary Segment. 39. What is a Data Segment ? Each Non-clustered table has a data segment. All of the table's data is stored in the extents of its data segment. Each cluster has a data segment. The data of every table in the cluster is stored in the cluster's data segment. 40. What is an Index Segment ? Each Index has an Index segment that stores all of its data. 41. What is Rollback Segment ? A Database contains one or more Rollback Segments to temporarily store "undo" information