Oracle DBA Troubleshooting Interview Questions - 1
What are dynamic performance views?
Dynamic performance views are also called V$ views. These views provided information about the sessions.
Any Oracle user can get information from dynamic performance views if the user has the select any table privilege. This privilege is generally granted through the SELECT_CATALOG_ROLE etc.
What is the use of ALERT log file?
The ALERT log is a log file that records database wide events.
The information in the ALERT log file is generally used for trouble shooting.
Following events are recorded in the ALERT log file:
Database shutdown and startup information
All non default parameters
Oracle internal (ORA – 600) errors
Information about a modified control file
At log switch
The location of ALERT log file is specified in the BACKGROUND_DUMP_DEST parameter.
What is the significance of latches with respect to performance tuning?
An Oracle process must acquire relevant latch in order to get resource allocated.
A latch is required for a very short amount of time to ensure that the resource is allocated.
Whenever there is a contention for latch, it indicates that there is a performance issue, which may be due to either of the two following reasons:
Lack of availability of resource
Poor application programming resulting in high number of requests for resource.
What are different types of locks?
There are two different types of locks, which are given as follows:
System locks – Held for a very brief period of time and controlled by Oracle.
User locks – Created and managed using dbms_lock package. Different types of user locks are given as follows:
The UL lock – Defined with the dbms_lock package.
The TX lock – Acquired once for every transaction. It is a row transaction lock.
The TM lock – Acquired once for each object, which is being changed. It is a DML lock. The IDI column identifies the object being modified.
Name three advisory statistics you can collect?
The three advisory statistics that can be collected are Buffer Cache, Advice, Segment Level Statistics and Timed Statistics.
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