Yes, there will be limits.. But the limits are high enough for practical purpose..
Participants can take several forms:
- Organizations with a separate identity and potentially with their own CA, MSP, orders, endorsers, and committers in any combination
- Roles in chaincodes
- Identities with a specific role in an organization
But you can set a small limit if you want..
And, there rollback (ACID compliant, example) if the submission of a transaction fails.
The rollback will only return a success or failure.. It does not make any changes of the failure on the ledger..
There are mainly two modes of failure:
- Fail during endorsement
- Fail during commit
To know more, you can go through http://hyperledger-fabric.readthedocs.io/en/latest/arch-deep-dive.html#basic-workflow-of-transaction-endorsement