switch from sybase to oracle - considerations?

I am in charge of a large J2EE application that utilizes Hibernate extensively at the DAO layer. I've recently been tasked to consider the repercussions and feasibility of switching from Sybase ASE 15 to Oracle 11g. What are some gotch-yas and future tasking that I'd need to keep in mind for a transition/migration such as this? Some quick things I've thought of are:

will 开发者_运维技巧our DAOs that utilize hibernate continue to work as is, or break?

how will we transfer all of the existing data?

data type mis matching between the two SQL servers ( sybase datatypes vs oracle datatypes )

Hard to answer your question without more detail of the size and so on, things will break so unless you have good tests avaliable you will need to create them before migration.

You should have a look at Oracle SQL Developer Migrations which would give you some hints and help you migrate SQLDDL and data and read the Sybase parts of the manuals avaliable at Database Migration Technology. Custom Java JDBC code or a ODBC connection and PL/SQL from Oracle can also be used to migrate the data see DG4ODBC.

It is straight forward to migrate compared to maintining multiple databases.

Thinking about my latest migration, the greatest pain was that Oracle is more kinky about connection resources, eg if you have resource leaks in your java code, it might not hurt your sybase instance but it WILL hurt your oracle instance. That said I don't think your hibernate DAOs have that problem.