Oracle Worldwide Technical Support answers approximately
questions a week
In the RDBMS support group we find there is often a common theme to the questions
Following are some of the most commonly asked questions and problems encountered in the RDBMS technical support group
These questions are based on problems encountered by relatively new DBA
s
Also included are answers and/or tools to help further identify the problem
Q
What should I do about this warning:
Warning in SQLPLUS
product information table not loaded
?
A
Run $ORACLE_HOME/sqlplus/admin/pupbld
sql as system (see appendix of sqlplus reference guide for details)
Q
How can users be restricted from issuing DML from SQLPLUS (when within
forms they are restricted but in SQLPLUS they aren
t)
A
Use the Product User Profile table in SQLPLUS (created by pupbld
sql
)
Q
Trying to restore from a full export and getting
duplicate key in
index
Why is this occurring?
A
The DB was not reinitialized before import
recreate DB
run catalog
sql and expvew
sql
Q
Why is performance slow on an particular application?
A
Run EXPLAIN PLAN and Tkprof to gather info about execution plan and some statistics (this doesn
t necessarily solve the problem but will help to identify it)
Q
Why is a tablespace that has been dropped still in the Data Dictionary?
A
It is probably in the DD as
invalid
will remain there unless the DB is reinitialized
Q
I can
t create objects in new tablespaces
What
s wrong?
A
Look in DBA_ROLLBACK_SEGS to be sure there are
rollback segments
If there isn
t create another (restart DB with it added to init
ora if it is private) before creating objects
Q
Why is the private rollback segment that was just created not being used?
A
If it is private it must be added to init
ora and the DB restarted before it will be acquired
Q
What do I do when an application is hanging?
A
Use SQLDBA Monitor Locks (also tables and processes) to determine if the table (or row) is locked and review tracefiles and alert
log for
errors (this doesn
t necessarily solve the problem but will help to identify it)
Q
How can you shrink a Rollback Segment?? (Or the variation: aren
t Rollback Segments deallocated?)
A
In V
rollback segments aren
t deallocated and you must drop and recreate to
shrink
them
in V
you can specify an
OPTIMAL SIZE
that the rollback segment will shrink to
Q
How do you move data from one tablespace to another?
A
See page
of the V
Utilities Guide (you need to revoke
grant
alter user
imp)
Q
Why is a created Public Rollback Segment not used by the application?
A
If transactions/transactions_per_rollback_segment is less than one than only one rollback_segment will be acquired and it will be system
Make the ration of the two be equal to the number of Rollback Segments
Q
The database is hanging
users can logon
but not do any work
What can I do?
A
Check whether the archiver is stuck (alert
log would show ORA
)
Either make space in the archival destination
or change the
log_archive_dest parameter
Q
How can I get a full error listing?
A
Add tracing to your session by issuing an
alter session set sql_trace true
Look for trace files in the USER_DUMP_DEST directory
Q
I removed the datafile before dropping the tablespace
How can I
recover from this ?
A
) shutdown
) startup mount
) alter database datafile
fullpath_of_removed_DF
offline drop
) alter database open
) drop tablespace ts_name including contents
Q
I have DBA privileges and still can
t connect internal
Why?
A
connect internal
is checked at the OS level
In Unix it means that your userid needs to be listed at the DBA group in the /etc/group file
Q
How can I create a copy of my database ?
A
Do a full export of the database
pre
create the second database including the needed tablespace
then perform full import
Q
Why are some tables missing from a full export ?
A
Objects owned by SYS are not exported
You shouldn
t be creating tables as sys
Q
Why is
Character type conversion
to
not supported
on an import?
A
That
s import telling you it
s trying to load a varchar into a char
You need to get a v
export of the v
database by using the v
export utility against the v
database:
) run
catexp
sql
as sys on the v
database (this will establish the views needed for a v
export
) From the v
set up TWO_TASK to point to the v
database
then perform the export
Q
What do I do if Drop tablespace is hanging in v
?
A
Make sure that the DC_ parameters are high enough
dc_free_extents > select count(*) from sys
fet$;
dc_used_extents > select count(*) from sys
uet$;
row_cache_enqueue >= dc_free_extents + dc_used_extents;
Q
How many blocks are actually used by the data in my tables ?
A
This query will count all the blocks occupied by the table
s data:
select count(distinct(substr(ROWID
) || (substr(ROWID
)) from
Q
How can I find all the duplicate entries in a table ?
A
select * from real_table_name X
where rowid < (select max(ROWID) from real_table_name where col
=l
and col
=l
) ;
From:http://tw.wingwit.com/Article/program/Oracle/201311/17311.html
