MBRC stands for what ?
-----Original Message-----
Sent: Tuesday, November 26, 2002 9:29 PM
To: Multiple recipients of list ORACLE-L
It's nice to know they have it now. I have one database on 9.2.0.2 but the
optimizer feature enable parameter is still on 8.1.7. We trying to reduce
the amount of work needed to downgrade in case we have to.
There are many problems we are working with Oracle to resolve.
Still my point is applicable regarding a big update using a PQO. The point
is all the parallel slaves work together to scan the segment/segments using
direct reads and then update the needed rows using rowid(no direct reads and
through the SGA).
This is very expensive and resource intensive when updating most of the
table.
The work around this, is many concurrent sessions, each running an update
statement with noparallel hint, and each updates a separate partition or
sub-segment.
Having or changing MBRC to a big setting would help.
Regards,
Waleed
-----Original Message-----
Sent: Tuesday, November 26, 2002 4:29 AM
To: Multiple recipients of list ORACLE-L
pdml on non-partitioned tables is there in 9i
hth
connor
- "Deshpande, Kirti" <kirti.deshpande_at_verizon.com>
wrote: > How true !! I just ignored the 'writing' part
of the
> parallelized 'reading'. Sorry.
> Thanks for catching it, Waleed.
> Our own update process, that I am baby sitting, was
> on my mind that involves a few partitioned tables...
>
>
> Regards,
>
> - Kirti
>
> -----Original Message-----
> Sent: Monday, November 25, 2002 9:09 PM
> To: Multiple recipients of list ORACLE-L
>
>
> PDML can be used only on partitioned segments. When
> PQO is used during an
> update on a non-partitioned segment, the parallel
> processes (slaves) work
> together to scan (read) the segment and find the
> rows that need to be
> updated. these rows get communicated back to the
> master process using the
> rowid. The master process starts to update rows
> serially using the rowid for
> update and this process could be slow and resources
> intensive specially when
> you are updating most of the rows in the table (you
> will see tons of db file
> sequential read).
>
> Regards,
>
> Waleed
>
> -----Original Message-----
> Sent: Monday, November 25, 2002 7:19 PM
> To: Multiple recipients of list ORACLE-L
>
>
> I would consider PDML to get the job done faster,
> provided there are enough
> resources.
> Using a cursor seems like a good idea, but avoid
> fetching across commits. We
> are going through a similar exercise, adding
> 10000000 to a cust_id field to
> denote the source of the data, and Developers
> complained about ORA-1555.
> Asked them not to commit as existing rollback
> segments and space were
> adequate ;)
>
> Good Luck,
>
> - Kirti
>
> -----Original Message-----
> Sent: Monday, November 25, 2002 3:04 PM
> To: Multiple recipients of list ORACLE-L
>
>
> I've got a real hot project (8.1.7.2 on HP/UX 11.0)
> that needs to have NULLs
> converted to spaces on three different columns.
> Each is a CHAR, so I
> shouldn't need to worry about chaining, since that
> column's full size has
> already been allocated in the block, right? But the
> first column has 1.2M
> NULLs out of 1.45M rows.
>
> My first test was to just UPDATE mytable SET mycol =
> ' ' WHERE mycol IS
> NULL, after removing the index on that column.
> Seeing as there were many
> more rows updated than I had anticipated, I was
> going to test the UPDATE
> using a cursor, and committing at every 10K rows
> (~120 total commits) to
> reduce rollback and locking issues.
>
> Thoughts? Since this table is used for
> time-and-attendance and directly
> affects payroll, downtime isn't possible.
>
> TIA!
>
> Rich
>
>
> Rich Jesse System/Database
> Administrator
> Rich.Jesse_at_qtiworld.com Quad/Tech
> International, Sussex, WI USA
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Received on Tue Nov 26 2002 - 11:24:06 CST
