40. Where can you get a list of all initialization parameters for your instance? How about an indication if they are default settings or have been changed

 

You can look in the init.ora file for an indication of manually set parameters. For all parameters, their value and whether or not the current value is the default value, look in the v$parameter view.

 

 

41. Describe hit ratio as it pertains to the database buffers. What is the difference between instantaneous and cumulative hit ratio and which should be used for tuning

 

The hit ratio is a measure of how many times the database was able to read a value from the buffers verses how many times it had to re-read a data value from the disks. A value greater than 80-90% is good, less could indicate problems. If you simply take the ratio of existing parameters this will be a cumulative value since the database started. If you do a comparison between pairs of readings based on some arbitrary time span, this is the instantaneous ratio for that time span. Generally speaking an instantaneous reading gives more valuable data since it will tell you what your instance is doing for the time it was generated over.

 

 

42. Discuss row chaining, how does it happen? How can you reduce it? How do you correct it

 

Row chaining occurs when a VARCHAR2 value is updated and the length of the new value is longer than the old value and won?t fit in the remaining block space. This results in the row chaining to another block. It can be reduced by setting the storage parameters on the table to appropriate values. It can be corrected by export and import of the effected table.

 

43. Give one method for transferring a table from one schema to another:

 

There are several possible methods, export-import, CREATE TABLE… AS SELECT, or COPY.

 

44. What is the purpose of the IMPORT option IGNORE? What is it?s default setting

 

The IMPORT IGNORE option tells import to ignore “already exists” errors. If it is not specified the tables that already exist will be skipped. If it is specified, the error is ignored and the tables data will be inserted. The default value is N.

 

 

45. You have a rollback segment in a version 7.2 database that has expanded beyond optimal, how can it be restored to optimal

 

Use the ALTER TABLESPACE ….. SHRINK command.

 

 

45. If the DEFAULT and TEMPORARY tablespace clauses are left out of a CREATE USER command what happens? Is this bad or good? Why

 

The user is assigned the SYSTEM tablespace as a default and temporary tablespace. This is bad because it causes user objects and temporary segments to be placed into the SYSTEM tablespace resulting in fragmentation and improper table placement (only data dictionary objects and the system rollback segment should be in SYSTEM).

 

 

46. What are some of the Oracle provided packages that DBAs should be aware of

 

Oracle provides a number of packages in the form of the DBMS_ packages owned by the SYS user. The packages used by DBAs may include: DBMS_SHARED_POOL, DBMS_UTILITY, DBMS_SQL, DBMS_DDL, DBMS_SESSION, DBMS_OUTPUT and DBMS_SNAPSHOT. They may also try to answer with the UTL*.SQL or CAT*.SQL series of SQL procedures. These can be viewed as extra credit but aren?t part of the answer.

 

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