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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Parallel index builds can crash
On a partitioned table? If you have a slave for each partition, how would this be wrong? Or, less slaves than partitions?
It was pounded into my head not to use parallel with non-partitioned tables because without partitions the slaves would not know how to divy up the work. Seemed to me that it should be smart enough to split it up by extents, but what do I know. Any comments?
I never did claim to be that incredibly bright and I did burn quite a few brain cells over the weekend. Forgive my ignorance, people ! We all have our days and then there are those of us who lie and claim not to.
-----Original Message-----
From: Tim Sawmiller [mailto:sawmillert_at_state.mi.us]
Sent: Monday, April 09, 2001 12:55 PM
To: Multiple recipients of list ORACLE-L
Subject: RE: Parallel index builds can crash
Well, duh, of course you're going to get 12 pieces, each of initial xxx size. How else can it do a parallel creation? Seems pretty intuitive to me...but then, I'm a pretty smart guy!
8-)
>>> lkoivu_at_qode.com 04/09/01 11:55AM >>> Hello Dick,
YOU ARE KIDDING. I've done this many times in the past and never encountered that type of behavior... I don't see what version/OS you are running? Was the table partitioned?
And, back by popular demand, is my highly overrated signature
Lisa Rutland Koivu
Oracle Database Administrator
lkoivu_at_qode.com
NeoMedia
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Enter Your PaperClick Code Here!
-----Original Message-----
Sent: Monday, April 09, 2001 11:41 AM
To: Multiple recipients of list ORACLE-L
To ALL,
Over the weekend I've been trying to rebuild a VERY large index on a
data
warehouse table. Well in an attempt to get faster processing I invoked the
parallel option, but the index failed for the one reason I could not easily
figure out. I expected the index to be 4 to 5 GB in size when completed,
but it
tried to create itself at 8 to 10 GB instead. Odd I thought until this
morning
when I noticed that there was two temporary segments in the target
tablespace.
I submitted a TAR to OTS for an explanation (Attached). Basically if you do
your index builds in parallel one should expect them to be the estimated
size
times the parallel setting. OOPS!!! :-( Someone can correct me if they
know
otherwise, but I don't remember seeing this in any of the documentation.
BTW: The final index size, now that it did successfully complete, is twice
what
I expected (parallel 2).
Dick Goulet
____________________Forward Header_____________________Author: rdbms4_at_us.oracle.com (Oracle Support) Date: 4/9/2001 10:33 AM
Hello Richard,
Creating Indexes in Parallel
Parallel index creation works in much the same way as a table scan with an
ORDER
BY clause. The table is randomly sampled and a set of index keys is found
that
equally divides the index into the same number of pieces as the degree of
parallelism(DOP). A first set of query processes scans the table, extracts
key,
ROWID pairs, and sends each pair to a process in a second set of query
processes
based on key. Each process in the second set sorts the keys and builds an
index
in the usual fashion.
After all index pieces are built, the parallel coordinator simply
concatenates
the pieces (which are ordered) to form the final index.
Parallel local index creation uses a single server set. Each server process
in
the set is assigned a table partition to scan, and
for which to build an index partition. Because half as many server processes
are
used for a given DOP, parallel local index
creation can be run with a higher DOP.
Note:
When creating an index in parallel, the STORAGE clause refers to
the
storage of each of the subindexes created by the query server
processes.
Therefore, an index created with an INITIAL
of 5MB and a DOP of 12 consumes at least 60MB of storage during
index
creation because each process starts with an extent of 5MB. When the
query
coordinator process combines the sorted subindexes, some of the extents
may
be trimmed, and the resulting index may be smaller than the requested
60MB.
ORA-1652
From version 7.x, we can create certain objects in parallel, or
unrecoverable.
In order for Oracle to accomplish this, temporary segments are created that
eventually become a permanent part of the object, yet Oracle still refers to
them as temp segments. Thus, most of the time you receive this error, it
will
be referring to the tablespace the object is going to be created in.
Do the following query to find out if you're out of extents:
select max(blocks), max (bytes) from sys.dba_free_space
where tablespace_name = '<tablespace in error message>';
For example, The above query may return:
SQL> blocks bytes
6143 12,580,864
Notice that the biggest CONTIGUOUS block of free space is only 6143 blocks
and
Oracle needs a contiguous block of free space of 6144 to create an object.
You may have a lot of free space in separate blocks in your tablespace, but
if
it is not contiguous, Oracle cannot use it. Allocating extents requires that
there be a contiguous block of free space.
SOLUTION:
1. Add a datafile to the tablespace
2. Adjust the storage parameters of the object you are trying to create.
Parameters to look at: initial extent, next extent, pct increase.
3. If you have a lot of free space in that tablespace, but the it is
very fragmented, you may want to consider rebuilding the tablespace.
4. Enable AUTOEXTEND for the datafile
- Also, Please review<Note:100492.1>Via metalink (Metalink - - >technical
library- - >reach with note#)
Title: ORA-01652: estimate space needed to create index
- Also further researched and found:<Bug:377439.-P>
Abstract: INDEX BUILD FAIL WITH PARALLEL DEGREE > 1
- is there any ora-7445 and core dump file in udump directory?
- is there an internal error (ora-600) trace file?
Please update the tar via metalink.
Thank you,
Oracle Support Services.
Have you tried MetaLink?
Search our technical libraries, create/review/update your TARs at:
http://metalink.oracle.com
-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author:Received on Mon Apr 09 2001 - 11:29:01 CDT
INET: dgoulet_at_vicr.com
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Tim Sawmiller
INET: sawmillert_at_state.mi.us
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