The following queries on the embedded PostreSQL will allow you to look for a specific string in all action payloads.
The queries are tested on NNM v10.00.
select *
from nms_action_command
where command like '%xxxx%' or command like '%xxxx%' or command like '%xxxx%' or command like '%xxxx%'
select *
from nms_incident_config
where description like '%xxxx%' or description like '%xxxx%' or description like '%xxxx%' or description like '%xxxx%'
or messageformat like '%xxxx%' or description like '%xxxx%' or description like '%xxxx%' or description like '%xxxx%'