CA Process Automation not raising new instances, or progressing existing ones.
PAM\server\c2o\logc2o.log file shows the error
Failed to publish message [...]
javax.jms.JMSException: The transaction log for database 'PAMRT' is full due to 'LOG_BACKUP'.
Release : 4.3
Component : Process Automation
The original cause was that the database transaction log filled for the PAMRT (Runtime) database in SQL Server. This was most likely due to a long running transaction and/or the need to take a log backup.
Once this had been performed, we then had to stop all four PAM nodes' services to free up the remaining DB locks in the system, as these were very long transactions to commit. After doing so, SQL Server could finish cleaning up the DB locks, and a restart got everything working again.
To ensure this doesn't happen again I would recommend the DBA check the SQL Server transaction log settings to ensure that space remains between log backups, or to set database recovery mode to 'simple'.