I am seeing a failure in HTTP API streaming ingestion - error message is - ECID not found (ECID is a primary identity).from where i need to change and are we need to connect anythng?

what is Nested fields,where we use ? 

at what time we need to craete batch and stream audience need to create ?why only we need to evening time?

how to find is this batch Ingestionand stream Ingestion  if u ingest data how system understood that batch or stream,what background process to run that ?and whre we see is this batch ingestion data and stream ingestion data like that ? if any one know can share the path or share the screen shot rea...

how to create realatinal schema ,and how to strich to main schema,and how to ingest dat separately or along with striching schema?which is better option?

what is main difference in unitary and business events in journey creation,and can send me on use for example,any source for to learn

in identity graph i don't want some data,so what are namespaces need to change connecting event data or need to remove the filed elements? 

in my interview i face this question ,can explain array methadology? in schema and how to manage this

if i want to connect cross chaneel ,what identity namespaces need to use and how to fix this?can explain ellabarative way?

if i want to ingest data ,but i don't want some data ,how?how to do conditinal ingestion ?  is this both are same or different?