Oracle DBA Interview Questions for Experienced Professionals - 2
Question: 6
What is a locally managed tablespace?
A locally managed tablespace keeps track of its own block and maintains the information in a bitmap in the header section rather than in the data dictionary.
Each bit in the bitmap corresponds to a block or a group of blocks.
When the extends are allocated or freed for reuse, Oracle changes the bitmap values to show the new status of the blocks.
These changes do not generate rollback information because they do not update tables in the data dictionary, unlike the default method of Dictionary – Managed Tablespace.
Question: 7
How would you force a log switch?
A log switch can be forced by using the ALTER SYSTEM SWITCH LOGFILE; statement.
Question: 8
What is row chaining?
Row chaining is a situation when a single row is stored in multiple blocks. It happens when row is too big to fit into a single block.
In other words, row chaining occurs when row size is greater than blocksize.
Tables with the LONG and LONG RAW columns are more likely to have chained rows.
In addition tables with more than 255 columns will have chained rows.
Question: 9
What is row migration?
Whenever a row length increase, as a result of an update and the current block is unable to provide additional space, the row has to be moved to another block with sufficient space.
In such situation , the original location of the row holds the rowid of the new location.
Question: 10
Explain the steps of creating copy of a control file?
Following are the steps to create a copy of control file.
Shutdown the database using the shutdown normal, shutdown immediate, or shutdown transactional command
Copy the control file to another disk using operating system’s file copy command.
Modify the CONTROL_FILE parameter in initialization parameter file to include additional control file.
Restart the instance
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