The first question that you should answer is: does it happen because of Siebel or the database?
To determine it, you can use a dedicated client with the SQL spool enabled, by adding the /s parameter to the command line in the shortcut. For example: D:\Siebel\Client\BIN\siebel.exe /c D:\Siebel\myConfig.cfg /s D:\Siebel\sql-spool.txt.
That way it will create a file with every SQL sentence being executed. This file will be quite big, so I suggest you to reproduce all the steps except the one causing trouble (open your Siebel client, navigate to the contacts screen, create a new record...), then open the SQL spool file in a text editor and position yourself at the end of the file. After that, click on the MVG field in Siebel, and refresh the spool file, to see what SQL sentences have been added.
The next step would be to launch the same sentences using a DB client (TOAD, Tora, SQL Plus...) and check if any of them takes too long to finish. You can access to the Oracle database administration console while doing so, and review the performance and the execution plan for each sentence, which can help you find what's causing the trouble. Most likely, you'll need to create an index for some columns.
If all the SQL sentences execute in a reasonable time, then you can discard the database and continue looking for problems in your SRF/repository:
- Do you have custom code in any business component or applet involved (contacts, addresses, etc.).
- Is your MVF field well defined? Is it vanilla or custom made?
- Are there user properties which apply to the MVG fields?
Try disabling any customisation you've made and check if it still happens with vanilla Siebel.