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Oracle 9i and Shrink Bloated Datafiles

Posted on 2006-11-07
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I have a DB (Oracle 9i) which has recently been growing at an exponential rate.  We finally found the source of the problem and have run the appropriate scripts to clear out the garbage data but now need to reclaim the ‘Whitespace’ in the data files.  I know that I can do an export of the DB then drop it and re-import but I was wondering if there is an easier way of dealing with this?  The problem is isolated to a single Tablespace / Datafile.

Thanks!
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Question by:Orwellian23
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rbrooker earned 250 total points
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Hi,

you can create a tablespace that is the size you think the problem tablespace should be and then move the segments from one to the other, rebuild the problem tablespace and move the segments back.

to move a table :
alter table my_table move tablespace <NEW_TABLESPACE>;
alter index my_index rebuild storage <NEW_TABLESPACE>;

( drop problem tablespace, rebuild problem tablespace )

alter table my_table move tablespace <ORIGINAL_TABLESPACE>;
alter index my_index rebuild storage <ORIGINAL_TABLESPACE>;

good luck :)

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by:Orwellian23
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The tablespace in question contains hundreds of tables, can every table be moved using a single command or would I need to run this Alter statement for each one?
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by:slightwv (䄆 Netminder)
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You can try resizing the datafile but I wouldn't hold out much hope of it being able to decrease the file much.

ALTER TABLESPACE <tablespace> RESIZE 80G;

I suggest just doing it in small chunks until you can't do it any more.

I think rbrooker's approach is the best.  Just write a SQL script to generate all the move commands, spool it out and execute the spooled file.

(untested):
-----------------
select 'alter table ' || table_name || ' move <NEW_TABLESPACE>;' from user_tables where tablespace_name='<OLD_TABLESPACE>';
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by:rbrooker
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Hi,

you can :

select 'alter table ' || table_name || ' move tablespace <NEW_TABLESPACE>;'
from dba_tables
where tablespace_name = '<ORIGINAL_TABLESPACE>';

select 'alter index ' || index_name || ' rebuild tablespace <NEW_TABLESPACE>;'
from dba_indexes
where tablespace_name = '<ORIGINAL_TABLESPACE>';

this will produce a list of tables that you can spool to a file and then run as a script.
note: if a table contains a LONG column, this will not work, and those tables will have to be exported and imported.  I am unsure on how LOBs will be treated as well.  this will get the majority tho, so what needs to be exported / imported may in fact be a very small list.
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by:Orwellian23
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Would that footnote also apply to BLOB datatypes?
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by:rbrooker
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I dont know, i do not deal with BLOBs / LOBs generally, it would probably be trial and error.
maybe there is another expert out there who knows?
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by:slightwv (䄆 Netminder)
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You should be able to move tables with LOB datatypes.  I don't have access to 9i any more but just tried it on 10.2 and it works just fine.
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by:gvsbnarayana
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Hi,
  You can try moving one by one like with the output of the query:
select 'alter table ' || owner || '.' || table_name || ' move tablespace NEW_TABLESPACE ;' || chr(10) ||
 'alter table ' || owner || '.' || table_name || ' move tablespace ORIGINAL_TABLESPACE ;'
from dba_tables where tablespace_name='ORIGINAL_TABLESPACE' ;
or you can use user_tables also.

In this case, your NEW tablespace should be big enough to hold the biggest table instead of all the tables at once.

HTH
Regards,
Badri.
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Expert Comment

by:suhong
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Just a try:

you can try alter table shrink space,
after coalesce the bloated  tablespaces
then then resize datafile.

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by:suhong
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Just a try:

you can try alter table shrink space,
after coalesce the bloated  tablespaces
then then resize datafile.
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by:slightwv (䄆 Netminder)
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suhong,

I don't have any 9i around to verify but I believe the 'shrink space' command is new to 10g.
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by:gvsbnarayana
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Shrink space is 10g command.. not in 9i.
You can use the MOVE clause of alter table .. to move the table to a different tablespace temporarily and then back to the original tablespace.
You can use alter table <table_name> move tablespace <tablespace>
This SQL will invalidate the indexes on the table and you will need to rebuild the same

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