This issues was faced by a developer, who asked for the solution, so here is something can be done at database level -
[a]
Create an Oracle profile and limit the number of sessions per database user, for example:

sql> CREATE PROFILE <profilename> limit SESSIONS_PER_USER 1;
sql> ALTER USER <username> <profilename>;
sql> ALTER SYSTEM SET RESOURCE_LIMIT=TRUE;
Using this approach, please be aware that dead connections will not always be detected by the database immediately, so users might occasionally not be able to login even a single time until a database administrator has killed their session. Also, …

Siebeldev.exe is a powerful utility provided in Siebel Tools, but don’t make full use of it. It can used to do some of our manual tasks of Tools like Import sifs, Export sifs, do Compilation, apply patches, all using the Commandline.

So, we can write a simple batch file with the Siebeldev.exe , its appropriate switches and parameters, and automate these tasks.

Automate Export Sifs from Siebel Tools:
1. Create a ExportSif.bat file.
2.Put below commandline in it and save the file.
c:\Sia80\Tools\BIN\siebdev.exe /c c:\Sia80\Tools\BIN\ENU\tools.cfg /u sadmin /p sadmin /d local /batchexport “Siebel Repository” C:\Sia80\Tools\bin\obj.txt …

Page#1
Goto URL – http://edelivery.oracle.com/
Click Continue button
Page#2
Give your name, company name, valid email id and country. Click Submit below.
Page#3
Select “Siebel CRM” from drop down and platform as “Microsoft Windows(32-bit)”. Click Continue.
Page#4
Search for “Siebel Business Applications Release 8.1.1.0 Media Pack for Microsoft Windows (32-bit)” on this page. Click that link.
Page#5
Look for Seconf Download button on the page. Or search “V14591-01″.
Here is your Siebel Bookshelf 8.1.1.0 Version.

Some people be wondering how does some screens have Icons, can we configure same for our custom screens??. I am referring to the icons similar to shown in the snap-shot below, like for Accounts, Contacts, Opportunities, Quotes.
Siebel Screen Icons
You can also put your custom icons to your custom screens by following the below procedure.
1. Get/Create your icon file and put it in the \Client\PUBLIC\enu\IMAGES folder. It should be in .gif format only. Say it, testicon.gif
2. Goto Tools -> Bitmap Categories.
3. Query for a existing Bitmap Category lets say – [Contact]
4. …

Sometimes you might need to add a extra Menu to Siebel Application. Lets say after “Help” menu as shown in the below screen shot.
Siebel Application Menus
Navigate to the Tools -> Application.
Locate your Siebel Application name, let’s say, [Siebel Universal Agent]
Go to its Menu field and get the Menu name, it might be [Generic WEB]
Now navigate to Tools -> Menu. Query the Menu as got above [Generic WEB]
Go to the child object Menu Items.
Now your new menu is going to come at 8th Position here as per above snapshot and there …