Data is read from the Content Services system into two groups for performance reasons. All metadata from the CS system is read into RAM at one time.
If other exported objects need this data, the data is placed in static storage. Other data that can be read and immediately written to Content Engine is considered transitory and is not retained after it is persisted to the Content Engine object store.
For performance reasons, the data that is read from the CS system by CS Export is separated into two groups. Some information is static and is held in memory for the duration of the migration. Other information is transitory and is written to Content Engine immediately after it is read.
Static data is composed of metadata and folder information that is very small in relation to the size taken up by the often large number of items and versions. Static data is referenced every time a document is added to Content Engine and is held in memory to facilitate faster access.
Static data is referenced every time an item and version's properties are enumerated, and it is for this reason that the static data is held in RAM for faster access.
Transitory data consists of the Item and Version CS objects only. Because of the potentially very large number of these types of objects, they are not retained in memory.