On Wed, 13 Nov 2002, [EMAIL PROTECTED] wrote:
> Are you sure about the "one round trip" thing.
Turns out you are right about not doing a single round-trip per row.
My information was either outdated or apocryphal:
SQL> select value from v$sesstat ss, v$statname sn where sid = 31 and
ss.statistic# = sn.statistic# and sn.name = 'SQL*Net roundtrips
to/from dblink';
VALUE
----------
0
SQL> insert into foobar (select * from foobar@baz);
1660073 rows created.
SQL> select value from v$sesstat ss, v$statname sn where sid = 31 and
ss.statistic# = sn.statistic# and sn.name = 'SQL*Net roundtrips
to/from dblink';
VALUE
----------
1925
(Oracle8i Enterprise Edition Release 8.1.7.3.0 - 64bit Production)
However, using DB links can never be as efficient as a parallel
datafile copy followed by a near-zero downtime switchover.
--
Jeremiah Wilton
http://www.speakeasy.net/~jwilton
> Hi Jeremiah
>
> Are you sure about the "one round trip" thing. I may be mistaken but I must
> admit that has not been my experience. Are you thinking of occasions when
> you use a remote table (accessible via a DBLink) in a local join? In such
> cases the optimizer might set up the plan to get the remote rows
> individually rather than doing unproductive remote full or range scans. One
> would anticipate that a query like INSERT into <localtable> (select * from
> remotetable@link) would pull things over in a stream. OCI certainly streams
> query results like that - I'm not saying that DBLinks are based on OCI -
> just that there is precedent for this in at least one Oracle networking
> layer.
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: Jeremiah Wilton
INET: [EMAIL PROTECTED]
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