please let me know the concept of TIERS in J2EE Is it a logical boundary or a physical boundary between layers. When i have webserver,application server and database server on same machine Is it a single tier or three tier? thanks Vikas
Hi Vikasids The tier model is the logical dividing of the three logical functions: presentation, business logic and data storage. Even when you are having it all on a single server, it will be possible to make a nice three tier model. BR Jan
A tier is generally a logical boundary, but a physical boundary could exist as well. For example, my servlets and jsps may represent a web tier of my application. My EJBs representing my business logic are the 2nd tier, and my database is my third tier. It doesn't really matter where my servers are running, you still have the logical separation of your code. If they are running on separate servers, then you have a physical boundary that maps to the logical boundary.
Q- Do Stored procedure and table data exist in different tier.? I remember reading a article which tells me SP are in a different tier than the database data. SP is in data access tier and data is in data tier.
Physically you can't separate stored procedures and the data as both are located in the database server (stored procedures are "installed" into the database similarly as records are inserted). Logically, however, the stored procedures belong to the business logic layer (or, if you prefer separating even more, to the data access layer).
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From the above clarifications can i make out one thing for sure that Tier architecture expands from n tier to n+1 in both horizontal and vertical directions. Lets say We have 3 separate layers(tiers) for respective presentation , business and data base related data case 1 if we break business layer in further two layers , we will call it n tier(3+1)solution.(vertical expansion) case 2 if we add another layer horizontally to presentation, business and database , again we will call it n tier(3+1) solution.
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