# Substation ES CICS Event Post Transaction

The following are Substation ES CICS Event Post Transactions located within the CICS region:

- `SXPT`: reliable transaction
- `SXPG`: guaranteed transaction
- `SXPO`: ordered transaction
- `SXPE`: error message transaction

When events are written to the outbound TDQ, those transactions are triggered. For the CICS Interface to be notified of outbound events, the CICS administrator must declare the transaction IDs in the TDQ definition. Through a Substation ES-supplied transaction class, the transactions ensure that only one of them is active within a CICS region at any time.

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