What is Sunopsis Memory Engine ?

Answer:- 

Actually Sunopsis Memory Engine is an In memory pure java based RDBMS. (hsqldb).

ODI provides Sunopsis Memory Engine as an in-memory database based on HSQLDB that serves quite well as a high-performing temporary data storage for intermediary data transformations. But, this engine is good for not too large set of data because it uses the memory from JVM that ODI runs on. For transformations of large data sets in interfaces, rather use an external RDBMS as the target or staging data-storage with truncate mode switched on . 

When you use the Sunopsis Memory Engine in an ODI interface or procedure an hsqldb in-memory database is created inside the JVM of the agent. The memory that is allocated to the hsqldb is taken from the JVM. As a result the maximum memory size that can be allocated to the in memory database is determined by the heap size parameter in the odiparams.bat file.