Getting the following error message when importing system definitions:

"CASRA0001E Field SYNCLEVEL value is invalid"

Example commands:

Export:
casrdtex /osystem_def.rdt /e /ip. /c /g

Import:
casrdtup /fsystem_def.rdt /op. /o

The error message "CASRA0001E Field SYNCLEVEL value is invalid" occurs because there is no SYNCLEVEL field in the (exported) definitions file.

In SEE6.0 SP1, support was added for EXEC CICS applications that start conversations with synclevel 2, thus the SYS definitions now need to have the SYNCLEVEL field.
SYNCLEVLEL is used in the definition of a Sys62 resource entry:
ESMAC->Resource->byType->Sys62->New Sys62
Connection Usage:
Transaction: Priority:
In Service: SYNCLEVEL: (1|2)

An export from an SEE6.0 SP1system does result in a file that can be imported without errors.
The problem occurs when the export is done from a system prior to SEE6.0 SP1

To solve this problem, either manually add the _SYNCLEVEL(x) field (where x=1 or 2) to the exported RDO file, or ensure all definitions are at the SEE6.0 SP1 level or higher before exporting them.

E.G. to manually add the _SYNCLEVEL(x) to an existing exported rdo file:
Edit the .rdt output file.
Add the SYNCLEVEL field at the end of all of the CONNECTION(S00n) records
For example if these records currently end with the "_MFPORT(nnnn)" field, that line should be updated to have:
_MFPORT(4725) _SYNCLEVEL(x)
(where x can be 1 or 2)

Additional information:
Whats New for SSEE6.0 SP1 … in a distributed synclevel 2 syncpoint conversation.
Add support for EXEC CICS applications that start conversations with synclevel 2.”
APPC only.
Leverage Microsoft Host Integration Server.
ES MSS “Sys62” connection definitions can now specify a synclevel value.
Existing Synclevel 1 behaviour should be unaffected.
Existing Synclevel 2 support using external RMs should be unaffected.