OMS Version 
OMS versions are only used by SAP liveCache database instances.
An OMS version is based on a consistent view and thus represents the consistent state of the SAP liveCache database instance, valid as of the time it started. An OMS version is generated by the application, and can extend across multiple transactions. It defines a range of data in which transactions can change objects independently of competing applications. At any particular time, one OMS version can be edited only within a database session.
An OMS version can be activated at any time in the Object Management System (OMS). All subsequent OMS operations refer to the activated OMS version. In particular, you can make changes that are visible only within the OMS view.
The data of each OMS version is copied to the OMS heap when it is read. The application decides whether the changes made to the objects within the OMS version are copied to the current state of the application. No changes to the data of an OMS version are copied to the data cache in any form without being requested by the application. This means that any data that the application does not copy to the current state is lost when an OMS version is deleted.
The previous OMS versions no longer exist after a restart. They are implicitly deleted.
When you close an OMS version (end a database session), the data can be swapped from the OMS heap to the data cache if memory bottlenecks occur.
See also:
Database Administration in CCMS: SAP liveCache Technology
OMS
Versions