[mapserver-users] SDE performance and error

[Andrea Goethals]

I thought the posting the other day about the performance of PostGIS
vs shapefiles was interesting. 

>>The PostGIS performance has been about 1/2 to 1/3 the speed as using
>>shapefiles on a RAID device.

I have been looking at shapefiles vs SDE and Oracle.

In that email Dave noted that there should be places where optimization
could take place. Similarly, I have been told that SDE and Oracle both
can be "tuned" (whatever that entails) to speed up the process. Neither
our SDE nor our Oracle has been tuned yet. Having said that it appears
that shapefiles are faster than SDE.

For initial testing purposes I accessed shapefiles on a different
machine
than mapserver was running on, which is the same machine the SDE server
is on. The Oracle 8.1.x is on a third machine.

-------------------       ---------------       ---------
 mapserver          |     |  shapefiles  |     |         |
                    | --- |              | --- | Oracle  |
 apache web server  |     |  SDE server  |     |         |
-------------------       ---------------       ---------
Linux                     Linux                Solaris

At the worst case SDE took 4 times longer than shapefiles. This seems
to occur for the larger datasets (ex: a shapefile of size:
12.6 MB .shp, 4.5 MB .dbf  took on average 10.5 seconds to access for an
SDE layer; 2.6 seconds for a shapefile)

For the smaller datasets and especially at smaller scales, the
difference 
between them is less.
(ex: a shapefile of size: 294 KB .shp, 419 KB .dbf took an average of
1.7 seconds for the SDE layer, and 1.3 seconds for the shapefile.)

I don't know if the slowdown is the communication between SDE and
Oracle,
the extra hop to the Oracle machine, or just SDE itself.



Beyond the speed issue, every once in a while I would get an error
trying
to access SDE layers, but only when trying to access the larger layers
(in filesize):
msSDELayerNextShape(): SDE error. SE_stream_fetch(): Network I/O error.
(-10)

According to the SDE book, an error code of -10 means that "a
catastrophic
error occurred during a client/server round-trip request and the
connection between the client task and the server was severed"

Is there a limit set somewhere as to how much data can be sent? No
errors
like this were found accessing the same datasets from ESRI's ArcView.

Anybody else getting this error?

Thanks,
Andrea

-- 
@-------------------------@
| Andrea Goethals         |
| andreag at geoplan.ufl.edu |
| GeoPlan Center          |
| University of Florida   |
@-------------------------@