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Home -> Community -> Mailing Lists -> Oracle-L -> Re:RE: Parallel index builds can crash
It is a normal behaviour for parallel query since 7.3.4.
Even table on which index being created has degree > 1 (suppose dgree 4)and
you create an index on that table, it will create initialy 4 extents of
initial extent size in target tablespace as well as 4 in temp table space to
develop that index. However once this job is completed , it will merge into
one or number of extents as per your storage parameter in target tablespace.
It is true for both creation of index as well as rebuilding index.
Regards
Rafiq
Reply-To: ORACLE-L_at_fatcity.com
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
Date: Mon, 09 Apr 2001 09:35:42 -0800
Lisa,
Regrettably I'm not kidding, and neither was OTS. I'm on HP-UX 10.20
Oracle
8.0.4.4.0. According to OTS this is the "normal" behavior for all versions
of
Oracle, on all platforms, that support parallel query. On a small index I
could
see one not noticing, but on what should be a 4 GB index one notices the
extra 4
GB that goes down the drain!
Dick Goulet
____________________Reply Separator____________________ Author: "Koivu; Lisa" <lkoivu_at_qode.com> Date: 4/9/2001 11:02 AM
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
2201 Second St., Suite 600
Fort Myers, FL 33901, USA
Phone: 941-337-3434
Fax: 941-337-3668
www.neom.com <http://www.neom.com> www.paperclick.com <http://www.paperclick.com> www.qode.com <http://www.qode.com>
P a p e r C l i c k . c o m <http://www.paperclick.com/home.htm>
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
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: 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). <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> <HTML> <HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=US-ASCII"> <META NAME="Generator" CONTENT="MS Exchange Server version 5.5.2653.12"> <TITLE>RE: Parallel index builds can crash</TITLE> </HEAD> <BODY> <P><FONT SIZE=2>Hello Dick, </FONT> </P> <P><FONT SIZE=2>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?</FONT></P> <P><FONT SIZE=2>And, back by popular demand, is my highly overrated signature</FONT> <BR><FONT SIZE=2> </FONT> <BR><FONT SIZE=2>Lisa Rutland Koivu</FONT> <BR><FONT SIZE=2>Oracle Database Administrator</FONT> <BR><FONT SIZE=2>lkoivu_at_qode.com</FONT> <BR><FONT SIZE=2> </FONT> <BR><FONT SIZE=2> NeoMedia</FONT> <BR><FONT SIZE=2> </FONT> <BR><FONT SIZE=2>2201 Second St., Suite 600</FONT> <BR><FONT SIZE=2>Fort Myers, FL 33901, USA</FONT> <BR><FONT SIZE=2>Phone: 941-337-3434</FONT> <BR><FONT SIZE=2>Fax: 941-337-3668</FONT> <BR><FONT SIZE=2>www.neom.com <<A HREF="http://www.neom.com" TARGET="_blank">http://www.neom.com</A>> </FONT> <BR><FONT SIZE=2>www.paperclick.com <<A HREF="http://www.paperclick.com" TARGET="_blank">http://www.paperclick.com</A>> </FONT> <BR><FONT SIZE=2>www.qode.com <<A HREF="http://www.qode.com" TARGET="_blank">http://www.qode.com</A>> </FONT> <BR><FONT SIZE=2> </FONT> <BR><FONT SIZE=2>P a p e r C l i c k . c o m <<A HREF="http://www.paperclick.com/home.htm" TARGET="_blank">http://www.paperclick.com/home.htm</A>> </FONT> <BR><FONT SIZE=2> </FONT> </P> <BR> <P><FONT SIZE=2> Enter Your PaperClick Code Here!</FONT> <BR><FONT SIZE=2> </FONT> <BR><FONT SIZE=2> </FONT> </P> <BR> <P><FONT SIZE=2>-----Original Message-----</FONT> <BR><FONT SIZE=2>From: dgoulet_at_vicr.com [<A HREF="mailto:dgoulet_at_vicr.com">mailto:dgoulet_at_vicr.com</A>]</FONT> <BR><FONT SIZE=2>Sent: Monday, April 09, 2001 11:41 AM</FONT> <BR><FONT SIZE=2>To: Multiple recipients of list ORACLE-L</FONT> <BR><FONT SIZE=2>Subject: Parallel index builds can crash</FONT> </P> <BR> <P><FONT SIZE=2>To ALL,</FONT> </P> <P><FONT SIZE=2> Over the weekend I've been trying to rebuild a VERY large index on a data</FONT> <BR><FONT SIZE=2>warehouse table. Well in an attempt to get faster processing I invoked the</FONT> <BR><FONT SIZE=2>parallel option, but the index failed for the one reason I could not easily</FONT> <BR><FONT SIZE=2>figure out. I expected the index to be 4 to 5 GB in size when completed, but it</FONT> <BR><FONT SIZE=2>tried to create itself at 8 to 10 GB instead. Odd I thought until this morning</FONT> <BR><FONT SIZE=2>when I noticed that there was two temporary segments in the target tablespace. </FONT> <BR><FONT SIZE=2>I submitted a TAR to OTS for an explanation (Attached). Basically if you do</FONT> <BR><FONT SIZE=2>your index builds in parallel one should expect them to be the estimated size</FONT> <BR><FONT SIZE=2>times the parallel setting. OOPS!!! :-( Someone can correct me if they know</FONT> <BR><FONT SIZE=2>otherwise, but I don't remember seeing this in any of the documentation.</FONT> </P> <P><FONT SIZE=2>BTW: The final index size, now that it did successfully complete, is twice what</FONT> <BR><FONT SIZE=2>I expected (parallel 2).</FONT> </P> <P><FONT SIZE=2>Dick Goulet</FONT> </P> <P><FONT SIZE=2>____________________Forward Header_____________________</FONT> <BR><FONT SIZE=2>Author: rdbms4_at_us.oracle.com (Oracle Support)</FONT> <BR><FONT SIZE=2>Date: 4/9/2001 10:33 AM</FONT> </P> <P><FONT SIZE=2> Hello Richard,</FONT> </P> <P><FONT SIZE=2>Creating Indexes in Parallel</FONT> </P> <P><FONT SIZE=2>Parallel index creation works in much the same way as a table scan with an ORDER</FONT> <BR><FONT SIZE=2>BY clause. The table is randomly sampled and a set of index keys is found that</FONT> <BR><FONT SIZE=2>equally divides the index into the same number of pieces as the degree of</FONT> <BR><FONT SIZE=2>parallelism(DOP). A first set of query processes scans the table, extracts key,</FONT> <BR><FONT SIZE=2>ROWID pairs, and sends each pair to a process in a second set of query processes</FONT> <BR><FONT SIZE=2>based on key. Each process in the second set sorts the keys and builds an index</FONT> <BR><FONT SIZE=2>in the usual fashion.</FONT> <BR><FONT SIZE=2>After all index pieces are built, the parallel coordinator simply concatenates</FONT> <BR><FONT SIZE=2>the pieces (which are ordered) to form the final index. </FONT> </P> <P><FONT SIZE=2>Parallel local index creation uses a single server set. Each server process in</FONT> <BR><FONT SIZE=2>the set is assigned a table partition to scan, and</FONT> <BR><FONT SIZE=2>for which to build an index partition. Because half as many server processes are</FONT> <BR><FONT SIZE=2>used for a given DOP, parallel local index</FONT> <BR><FONT SIZE=2>creation can be run with a higher DOP. </FONT> </P> <P><FONT SIZE=2> Note: </FONT> </P> <P><FONT SIZE=2> When creating an index in parallel, the STORAGE clause refers to the</FONT> <BR><FONT SIZE=2>storage of each of the subindexes created by the query server processes.</FONT> <BR><FONT SIZE=2>Therefore, an index created with an INITIAL</FONT> <BR><FONT SIZE=2> of 5MB and a DOP of 12 consumes at least 60MB of storage during index</FONT> <BR><FONT SIZE=2>creation because each process starts with an extent of 5MB. When the query</FONT> <BR><FONT SIZE=2>coordinator process combines the sorted subindexes, some of the extents may</FONT> <BR><FONT SIZE=2>be trimmed, and the resulting index may be smaller than the requested 60MB. </FONT> </P> <BR> <P><FONT SIZE=2>ORA-1652</FONT> <BR><FONT SIZE=2>From version 7.x, we can create certain objects in parallel, or unrecoverable. </FONT> <BR><FONT SIZE=2>In order for Oracle to accomplish this, temporary segments are created that </FONT> <BR><FONT SIZE=2>eventually become a permanent part of the object, yet Oracle still refers to </FONT> <BR><FONT SIZE=2>them as temp segments. Thus, most of the time you receive this error, it will </FONT> <BR><FONT SIZE=2>be referring to the tablespace the object is going to be created in. </FONT> </P> <P><FONT SIZE=2>Do the following query to find out if you're out of extents: </FONT> <BR><FONT SIZE=2> </FONT> <BR><FONT SIZE=2> select max(blocks), max (bytes) from sys.dba_free_space </FONT> <BR><FONT SIZE=2> where tablespace_name = '<tablespace in error message>'; </FONT> <BR><FONT SIZE=2> </FONT> <BR><FONT SIZE=2>For example, The above query may return:</FONT> <BR><FONT SIZE=2> SQL> blocks bytes </FONT> <BR><FONT SIZE=2> 6143 12,580,864 </FONT> <BR><FONT SIZE=2> </FONT> <BR><FONT SIZE=2>Notice that the biggest CONTIGUOUS block of free space is only 6143 blocks and </FONT> <BR><FONT SIZE=2>Oracle needs a contiguous block of free space of 6144 to create an object. </FONT> <BR><FONT SIZE=2> </FONT> <BR><FONT SIZE=2>You may have a lot of free space in separate blocks in your tablespace, but if </FONT> <BR><FONT SIZE=2>it is not contiguous, Oracle cannot use it. Allocating extents requires that </FONT> <BR><FONT SIZE=2>there be a contiguous block of free space. </FONT> </P> <BR> <P><FONT SIZE=2>SOLUTION: </FONT> <BR><FONT SIZE=2>1. Add a datafile to the tablespace </FONT> <BR><FONT SIZE=2>2. Adjust the storage parameters of the object you are trying to create. </FONT> <BR><FONT SIZE=2> Parameters to look at: initial extent, next extent, pct increase. </FONT> <BR><FONT SIZE=2>3. If you have a lot of free space in that tablespace, but the it is </FONT> <BR><FONT SIZE=2> very fragmented, you may want to consider rebuilding the tablespace. </FONT> <BR><FONT SIZE=2>4. Enable AUTOEXTEND for the datafile </FONT> </P> <BR> <P><FONT SIZE=2> </FONT> </P> <P><FONT SIZE=2> - Also, Please review<Note:100492.1>Via metalink (Metalink - - >technical</FONT> <BR><FONT SIZE=2>library- - >reach with note#)</FONT> <BR><FONT SIZE=2>Title: & nbsp; ORA-01652: estimate space needed to create index</FONT> </P> <BR> <BR> <BR> <P><FONT SIZE=2> - Also further researched and found:<Bug:377439.-P> </FONT> <BR><FONT SIZE=2>Abstract: INDEX BUILD FAIL WITH PARALLEL DEGREE > 1</FONT> </P> <BR> <BR> <P><FONT SIZE=2> - is there any ora-7445 and core dump file in udump directory?</FONT> <BR><FONT SIZE=2> - is there an internal error (ora-600) trace file?</FONT> </P> <P><FONT SIZE=2>Please update the tar via metalink.</FONT> <BR><FONT SIZE=2> Thank you,</FONT> <BR><FONT SIZE=2>Oracle Support Services.</FONT> <BR><FONT SIZE=2> </FONT> <BR><FONT SIZE=2> </FONT> <BR><FONT SIZE=2> </FONT> <BR><FONT SIZE=2>Have you tried MetaLink? </FONT> <BR><FONT SIZE=2>Search our technical libraries, create/review/update your TARs at: </FONT> <BR><FONT SIZE=2><A HREF="http://metalink.oracle.com" TARGET="_blank">http://metalink.oracle.com</A> </FONT> </P> <BR> <P><FONT SIZE=2>-- </FONT> <BR><FONT SIZE=2>Please see the official ORACLE-L FAQ: <A HREF="http://www.orafaq.com" TARGET="_blank">http://www.orafaq.com</A></FONT> <BR><FONT SIZE=2>-- </FONT> <BR><FONT SIZE=2>Author: </FONT> <BR><FONT SIZE=2> INET: dgoulet_at_vicr.com</FONT> </P> <P><FONT SIZE=2>Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051</FONT> <BR><FONT SIZE=2>San Diego, California -- Public Internet access / Mailing Lists</FONT> <BR><FONT SIZE=2>--------------------------------------------------------------------</FON T> <BR><FONT SIZE=2>To REMOVE yourself from this mailing list, send an E-Mail message</FONT> <BR><FONT SIZE=2>to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in</FONT> <BR><FONT SIZE=2>the message BODY, include a line containing: UNSUB ORACLE-L</FONT> <BR><FONT SIZE=2>(or the name of mailing list you want to be removed from). You may</FONT> <BR><FONT SIZE=2>also send the HELP command for other information (like subscribing).</FONT> </P> </BODY> </HTML> -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: 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). _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Mohammad Rafiq INET: rafiq9857_at_hotmail.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).Received on Mon Apr 09 2001 - 14:20:34 CDT
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