Do other RDMS have clustered indexes?

i realize the term "clustered index" is a MS thing. i also know that the
clustered index is the physical sort order of data in a table. And once i
have this technique available to me, i can take advantage of it to group
low-cardinality rows together, where an index would not be selective enough.
So, with clustered indexes in SQL Server, i have another performance tuning
option. Does Oracle, MySQL, DB2 let the user change the physical sort order
of a table - and be able to take advantage of that for query optimization?I recall a long long time ago working with the OS/2 version of DB2 (DB2/2):
You did a rebuild of the table to cluster it. This was a once operation. At the end of the table
(imagine pages and extents), you had overflow pages. New rows were not inserted in place, but were
added to these overflow pages. So, you didn't get the fragmentation aspects of SQL Server, but there
was some extra cost for looking up these overflow pages.
All above is from memory, from around 1991. This might have been special to the OS/2 version of DB2,
and/or it might have been changed since.
--
Tibor Karaszi, SQL Server MVP
http://www.karaszi.com/sqlserver/default.asp
http://www.solidqualitylearning.com/
"Ian Boyd" <ian.msnews010@.avatopia.com> wrote in message
news:%235qm3VU5FHA.3532@.TK2MSFTNGP10.phx.gbl...
>i realize the term "clustered index" is a MS thing. i also know that the clustered index is the
>physical sort order of data in a table. And once i have this technique available to me, i can take
>advantage of it to group low-cardinality rows together, where an index would not be selective
>enough.
> So, with clustered indexes in SQL Server, i have another performance tuning option. Does Oracle,
> MySQL, DB2 let the user change the physical sort order of a table - and be able to take advantage
> of that for query optimization?
>|||With DB2 you can create a single clustered index on a table and specify
whether or not you want it ASC or DESC. You can also specify to either
allow or disallow Reverse Scans.
In addition DB2 v. 8.2 has added functionality to eliminate the limit
of one clustered index per table. They have what is call an MDC (Multi
Dimensional Cluster) which allows you to effectively create more than
one clustered index on a single table. They do this by arranging the
data into blocks rather than index pages. The are extremely effective
in performance tuning where you have a large data set.|||Oracle's Index Organized tables aka IOT are quite similar to MS SQL
Servers clustered index.
DB2's clustered index and its table are separate objects. The docs used
to say that DB2 will try to maintain physical order, but there was no
guarantee - you needed to reorganize the table periodically once the
clustering factor dropped too low. ("clustering factor" is statistics
present in DB2 and Oracle, but not relevant to MS SQL Server, because
MS SQL Server uses bookmarks, not Row identifiers to locate a row from
a non-clustered index)|||"Ian Boyd" <ian.msnews010@.avatopia.com> wrote in message
news:%235qm3VU5FHA.3532@.TK2MSFTNGP10.phx.gbl...
>i realize the term "clustered index" is a MS thing. i also know that the
>clustered index is the physical sort order of data in a table. And once i
>have this technique available to me, i can take advantage of it to group
>low-cardinality rows together, where an index would not be selective
>enough.
> So, with clustered indexes in SQL Server, i have another performance
> tuning option. Does Oracle, MySQL, DB2 let the user change the physical
> sort order of a table - and be able to take advantage of that for query
> optimization?
In Oracle an "Index-Organized Table" is the equivalent as a SQL Server
clustered index. There are some minor differences in implementation, for
instance, the requirement that the "clustered index" must be the primary
key. But they are pretty much the same thing.
David|||Alexander Kuznetsov wrote:
> Oracle's Index Organized tables aka IOT are quite similar to MS SQL
> Servers clustered index.
> DB2's clustered index and its table are separate objects. The docs
> used to say that DB2 will try to maintain physical order, but there
> was no guarantee - you needed to reorganize the table periodically
> once the clustering factor dropped too low. ("clustering factor" is
> statistics present in DB2 and Oracle, but not relevant to MS SQL
> Server, because MS SQL Server uses bookmarks, not Row identifiers to
> locate a row from a non-clustered index)
MaxDB has a similar feature: *all* tables are stored the way MS SQL Server
tables with a clustered index are stored. The index used is the PK of the
table and if there is no PK then a hidden column with a synthetic value is
added and used for the PK.
Kind regards
robert

Do other RDMS have clustered indexes?

i realize the term "clustered index" is a MS thing. i also know that the
clustered index is the physical sort order of data in a table. And once i
have this technique available to me, i can take advantage of it to group
low-cardinality rows together, where an index would not be selective enough.
So, with clustered indexes in SQL Server, i have another performance tuning
option. Does Oracle, MySQL, DB2 let the user change the physical sort order
of a table - and be able to take advantage of that for query optimization?I recall a long long time ago working with the OS/2 version of DB2 (DB2/2):
You did a rebuild of the table to cluster it. This was a once operation. At
the end of the table
(imagine pages and extents), you had overflow pages. New rows were not inser
ted in place, but were
added to these overflow pages. So, you didn't get the fragmentation aspects
of SQL Server, but there
was some extra cost for looking up these overflow pages.
All above is from memory, from around 1991. This might have been special to
the OS/2 version of DB2,
and/or it might have been changed since.
Tibor Karaszi, SQL Server MVP
http://www.karaszi.com/sqlserver/default.asp
http://www.solidqualitylearning.com/
"Ian Boyd" <ian.msnews010@.avatopia.com> wrote in message
news:%235qm3VU5FHA.3532@.TK2MSFTNGP10.phx.gbl...
>i realize the term "clustered index" is a MS thing. i also know that the cl
ustered index is the
>physical sort order of data in a table. And once i have this technique avai
lable to me, i can take
>advantage of it to group low-cardinality rows together, where an index woul
d not be selective
>enough.
> So, with clustered indexes in SQL Server, i have another performance tunin
g option. Does Oracle,
> MySQL, DB2 let the user change the physical sort order of a table - and be
able to take advantage
> of that for query optimization?
>|||With DB2 you can create a single clustered index on a table and specify
whether or not you want it ASC or DESC. You can also specify to either
allow or disallow Reverse Scans.
In addition DB2 v. 8.2 has added functionality to eliminate the limit
of one clustered index per table. They have what is call an MDC (Multi
Dimensional Cluster) which allows you to effectively create more than
one clustered index on a single table. They do this by arranging the
data into blocks rather than index pages. The are extremely effective
in performance tuning where you have a large data set.|||Oracle's Index Organized tables aka IOT are quite similar to MS SQL
Servers clustered index.
DB2's clustered index and its table are separate objects. The docs used
to say that DB2 will try to maintain physical order, but there was no
guarantee - you needed to reorganize the table periodically once the
clustering factor dropped too low. ("clustering factor" is statistics
present in DB2 and Oracle, but not relevant to MS SQL Server, because
MS SQL Server uses bookmarks, not Row identifiers to locate a row from
a non-clustered index)|||"Ian Boyd" <ian.msnews010@.avatopia.com> wrote in message
news:%235qm3VU5FHA.3532@.TK2MSFTNGP10.phx.gbl...
>i realize the term "clustered index" is a MS thing. i also know that the
>clustered index is the physical sort order of data in a table. And once i
>have this technique available to me, i can take advantage of it to group
>low-cardinality rows together, where an index would not be selective
>enough.
> So, with clustered indexes in SQL Server, i have another performance
> tuning option. Does Oracle, MySQL, DB2 let the user change the physical
> sort order of a table - and be able to take advantage of that for query
> optimization?
In Oracle an "Index-Organized Table" is the equivalent as a SQL Server
clustered index. There are some minor differences in implementation, for
instance, the requirement that the "clustered index" must be the primary
key. But they are pretty much the same thing.
David|||Alexander Kuznetsov wrote:
> Oracle's Index Organized tables aka IOT are quite similar to MS SQL
> Servers clustered index.
> DB2's clustered index and its table are separate objects. The docs
> used to say that DB2 will try to maintain physical order, but there
> was no guarantee - you needed to reorganize the table periodically
> once the clustering factor dropped too low. ("clustering factor" is
> statistics present in DB2 and Oracle, but not relevant to MS SQL
> Server, because MS SQL Server uses bookmarks, not Row identifiers to
> locate a row from a non-clustered index)
MaxDB has a similar feature: *all* tables are stored the way MS SQL Server
tables with a clustered index are stored. The index used is the PK of the
table and if there is no PK then a hidden column with a synthetic value is
added and used for the PK.
Kind regards
robert

Do other RDMS have clustered indexes?

i realize the term "clustered index" is a MS thing. i also know that the
clustered index is the physical sort order of data in a table. And once i
have this technique available to me, i can take advantage of it to group
low-cardinality rows together, where an index would not be selective enough.
So, with clustered indexes in SQL Server, i have another performance tuning
option. Does Oracle, MySQL, DB2 let the user change the physical sort order
of a table - and be able to take advantage of that for query optimization?
I recall a long long time ago working with the OS/2 version of DB2 (DB2/2):
You did a rebuild of the table to cluster it. This was a once operation. At the end of the table
(imagine pages and extents), you had overflow pages. New rows were not inserted in place, but were
added to these overflow pages. So, you didn't get the fragmentation aspects of SQL Server, but there
was some extra cost for looking up these overflow pages.
All above is from memory, from around 1991. This might have been special to the OS/2 version of DB2,
and/or it might have been changed since.
Tibor Karaszi, SQL Server MVP
http://www.karaszi.com/sqlserver/default.asp
http://www.solidqualitylearning.com/
"Ian Boyd" <ian.msnews010@.avatopia.com> wrote in message
news:%235qm3VU5FHA.3532@.TK2MSFTNGP10.phx.gbl...
>i realize the term "clustered index" is a MS thing. i also know that the clustered index is the
>physical sort order of data in a table. And once i have this technique available to me, i can take
>advantage of it to group low-cardinality rows together, where an index would not be selective
>enough.
> So, with clustered indexes in SQL Server, i have another performance tuning option. Does Oracle,
> MySQL, DB2 let the user change the physical sort order of a table - and be able to take advantage
> of that for query optimization?
>
|||With DB2 you can create a single clustered index on a table and specify
whether or not you want it ASC or DESC. You can also specify to either
allow or disallow Reverse Scans.
In addition DB2 v. 8.2 has added functionality to eliminate the limit
of one clustered index per table. They have what is call an MDC (Multi
Dimensional Cluster) which allows you to effectively create more than
one clustered index on a single table. They do this by arranging the
data into blocks rather than index pages. The are extremely effective
in performance tuning where you have a large data set.
|||Oracle's Index Organized tables aka IOT are quite similar to MS SQL
Servers clustered index.
DB2's clustered index and its table are separate objects. The docs used
to say that DB2 will try to maintain physical order, but there was no
guarantee - you needed to reorganize the table periodically once the
clustering factor dropped too low. ("clustering factor" is statistics
present in DB2 and Oracle, but not relevant to MS SQL Server, because
MS SQL Server uses bookmarks, not Row identifiers to locate a row from
a non-clustered index)
|||"Ian Boyd" <ian.msnews010@.avatopia.com> wrote in message
news:%235qm3VU5FHA.3532@.TK2MSFTNGP10.phx.gbl...
>i realize the term "clustered index" is a MS thing. i also know that the
>clustered index is the physical sort order of data in a table. And once i
>have this technique available to me, i can take advantage of it to group
>low-cardinality rows together, where an index would not be selective
>enough.
> So, with clustered indexes in SQL Server, i have another performance
> tuning option. Does Oracle, MySQL, DB2 let the user change the physical
> sort order of a table - and be able to take advantage of that for query
> optimization?
In Oracle an "Index-Organized Table" is the equivalent as a SQL Server
clustered index. There are some minor differences in implementation, for
instance, the requirement that the "clustered index" must be the primary
key. But they are pretty much the same thing.
David
|||Alexander Kuznetsov wrote:
> Oracle's Index Organized tables aka IOT are quite similar to MS SQL
> Servers clustered index.
> DB2's clustered index and its table are separate objects. The docs
> used to say that DB2 will try to maintain physical order, but there
> was no guarantee - you needed to reorganize the table periodically
> once the clustering factor dropped too low. ("clustering factor" is
> statistics present in DB2 and Oracle, but not relevant to MS SQL
> Server, because MS SQL Server uses bookmarks, not Row identifiers to
> locate a row from a non-clustered index)
MaxDB has a similar feature: *all* tables are stored the way MS SQL Server
tables with a clustered index are stored. The index used is the PK of the
table and if there is no PK then a hidden column with a synthetic value is
added and used for the PK.
Kind regards
robert

Distributed Transactions ?

Hi There

I realize this is probably a basic question or at least i hope so but i cannot get distributed transactions working.

BOL is just driving me in circles.
I am running SS2000, MSDTC is up and running on the server.

I have added a trigger to a table where on insert or update the triggers fires and inserts a row to a remote server.

When i execute the update or insert i get the error:
Cannot start a distributed transaction.

I have tried stating BEGIN DISTRIBUTED TRANSACTION before the update but i get the same error, i have also read up on SET REMOTE_PROC_TRANSACTIONS, but this is not a remote sp.

Can anyone please reccomend a good link as to how to get distributed transactions to work.

Thanx
P.S I have already checked this link http://support.microsoft.com/?kbid=816701.

Also i have found references to checking avrious services are running etc, seems there is alot to setup to get MSDTC to work but i cannot find the setup in BOL, not sure everything i have to do to egt MSDTC to work ?

Please help Thanx
|||

Have you tried setting XACT_ABORT ton ON?

Denis the SQL Menace

http://sqlservercode.blogspot.com/

|||Hi

Tried this

SET XACT_ABORT ON
BEGIN DISTRIBUTED TRANSACTION
UPDATE PSAPMSGSUBCON SET STATUSSTRING = 'ERROR'

Got this error:

[OLE/DB provider returned message: New transaction cannot enlist in the specified transaction coordinator. ]
OLE DB error trace [OLE/DB Provider 'SQLOLEDB' ITransactionJoin::JoinTransaction returned 0x8004d00a].
Msg 7391, Level 16, State 1, Procedure PSAPMSGSUBCON_MESSAGE_ERROR_TRIGGER, Line 11
The operation could not be performed because the OLE DB provider 'SQLOLEDB' was unable to begin a distributed transaction.

ALso found this in BOL:

It is required that XACT_ABORT be set ON for data modification statements in an implicit or explicit transaction against most OLE DB providers, including SQL Server. The only case where this option is not required is if the provider supports nested transactions. For more information, see Distributed Queries and Distributed Transactions.

I think i am simply missing something to ensure MSDTC is setup and running correctly.
Is the only thing require for MSDTC to work , that it be running, servers have the network DTC enabled and you stipulate

BEGIN DISTRIBUTED TRANSACTION

?