I created my workrep based on oracle datbase and in the topology section in Physical Architecture pane I can see Oracle .
Now when i got to the section below it "Logical Architecture" and right click to chose create new logical schema it opens a new wizard.
in which context is global and on the right side in the physical schemas it says <Undefined> as the only value.
So, how to fix it to associate it with the physical schema?
You will first need to create a Data Server and Physical Schema under the Physical Architecture section and Oracle technology. You can then select the Physical Schema in the Logical Schema - context mapping. See the docs here: http://docs.oracle.com/cd/E23943_01/integrate.1111/e12643/setup_topology.htm#CHDCEADA
Or you can directly provide the logical schema while creating the physical schema under data server. Select the context tab and give the logical schema name. Save it.
When you will check the logical architecture you will find the logical schema name already created and linked with the physical schema .
is it ok to provide same schema name for work and data schema? Or these two must be different? what will happen if same is specified will it ODI be able to create temp tables without any problems like name conflict etc?
The same schema is fine. There should be no name conflicts as ODI uses the prefix I$, C$, E$, etc for the temporary tables. If you use the same work schema across multiple schemas that have tables with the same name, you will run into naming issues, so beware of this. For example:
HR schema has table PERSON.
CONTRACT schema also has table PERSON.
If EDW_STG is the work schema for both HR and CONTRACT, ODI will attempt to create I$_PERSON when either of the PERSON tables is being loaded by an ODI Interface.
so after doing this part i went on to model in designer tab and choose create a new model and went to reverse engineer after selecting table and view. On clicking reverse engineer its showing a popup title "Starting ODI action" please wait... from last more than 15 min. is it normal?
That is not normal. Lots of different things to check, but start with ensuring the Data server connection is setup correctly (correct port, user, etc). If you are working across a VPN connection, you may see a significant delay (as I often do).