Our object is to use medium server farm and configure server as both search queries and indexing server.
1. Make sure indexing service is started.
2. Go to Central Administration > Operations > topologies and services > Services on Server
Here we see five options:
Single Server or Web Server for small server farms (All services run on this server)
Web Server for medium server farms (Web application and Search Query services run on this server)
Search Indexing(Search Indexing service runs on this server)
Excel Calculation(Excel Calculation service runs on this server)
Custom (Services you choose run on this server)
3. Click “Office SharePoint Server Search”.
Select both checkboxes.
4. Set proper user.
Note: User must have sufficient privileges to access the SQL Server database.
Now your server is configured for both search queries and indexing server.