Oracle DBA Interview Questions for Experienced Professionals - 1

Question: 1

What are online redo log files?

Redo log files are the disk resources to store data changes.

Whenever data is changed, the information about the change is stored in the redo log file. It helps in recovery.

Question: 2

What is archive log file?

Archive log file stores redo log information persistently.

A redo log is overwritten with time; therefore, archive log maintains that lost information.

Question: 3

What is PCTFREE?

PCTUSED is a parameter that is used to specify the percentage required for a block to be considered as used.

The default value of this parameter is 40, which means that a block is considered to be used when it is more than 40% full and cannot be added to a freelist.

Question: 4

What is a log switch?

A log switch is a point when LoG Writer (LGWR) files one online redo log group and starts writing to another.

At every log switch a checkpoint occurs.

Question: 5

What is checkpoint?

A checkpoint is a point when a background process updates the headers of all datafiles and control files to synchronize the files.

At checkpoint, DataBase Writer (DBWR) writes the dirty buffers to the datafile.