Contact With Server Lost? error

Question

I have a workbook that contains several tabs. One of these tabs runs a query that displays approximately 4000 rows and about 100 columns. Although it took a full 2 minutes to run, the results were displayed. Recently however I encounter an error message that the page cannot be displayed and contact with the server has been lost. No results are displayed at all but I can the results if I export to Excel.
The Excel export is my short term workaround. I've noticed that if cut down the number of rows returned to 50 or even 25 that it runs properly but anthing reaching towards 100 rows per page will result in nothing displayed. Is there a buffer or something on the server side that I can increase or clear out? This report will only get larger over time so a short term and a long term solution would be appreciated.
ALSO: Does Discoverer support the STRAGG function?
Thanks

Answer 1

Hi Marcus
You have a number of questions here so let me try and give you some overall guidelines concerning performance.
1. Tables perform better than Crosstabs
2. Worksheets that contain Page Items perform worse than those than do not contain Page Items
3. Page Items that contain lots of items perform worse than Page Items that contain a small number of items
4. Complex folders perform worse than simple folders
5. Worksheets with lots of columns perform worse than those with fewer columns
6. The placement of data items in the Admin edition is important. In order of optimum performance place item here:
a) Side
b) Top of Side
c) Top
d) Page
7. Avoid very wide Crosstabs if humanly possible
8. Do not leave a workbook with partial drills, make sure all drills are collapsed
9. Parameters improve performance
10. Try to avoid worksheets that return in excess of 10,000 rows
11. Avoid calculations such as UPPER(:region) IN UPPER(region). If you are certain that an item is in uppercase then define it as such in the Admin edition and then only apply the UPPER to the parameter
12. Avoid worksheets that contain fan traps as these seriously impact performance
13. Do not create LOVs out of transactional tables. Rather you should define a LOV using special custom code
14. If you know SQL at all, examine your worksheet SQL in Explain Plan and see if there are any full table scans going on. If there are, fix them. You may need to create a view for this.
Ok, now that I have got the basics of performance out of the way, over to your particular issues. I have seen Contact with Server Lost messages continually ever since Discoverer first came out during the mid-1990s. This error normally happens in Desktop and is usually associated with either a genuine network issue or an out of memory situation. I wuold think that if you have 4000 rows and 100 columns that you might be pushing your luck if you don't have a lot of memory.
If you are using Plus or Viewer try setting the page size to 20 rows at a time. You can also try setting the number of rows returned to a lower number.
As for the STRAGG function. Discoverer can operate with any function providing that the function is either a) a standard SQL function existing within the database, or b) a user-defined function that has been imported into Discoverer and registered with the EUL. If you are able to go to SQL, type something like SELECT STRAGG('ABC') from dual and get an answer then this can be made available inside Discoverer.
The normal STRAGG function outlined below:
CREATE or replace FUNCTION stragg(input varchar2 )
RETURN varchar2
PARALLEL_ENABLE AGGREGATE USING string_agg_type;
is a user-defined function and would need to be registered with the EUL before it could be used within a Discoverer workbook.
Hope this helps
Regards
Michael