What kind of indexes are idx, sidx?

[chaseto]

| eventcount summarize=false index=* | dedup index | fields index

I used the above search to list all the indexes in my environment and found files like 123_xxx_xxxx_idx, 123_xxx_xxxx_sdx,

[lguinn2]

If they show up in as an index in your search results, then you should be able to examine them under Settings > Indexes. You can also search them: index=123* would do it.

I don't believe that Splunk would create index names or file names like these. So they were created by someone or some process on your system.

if they are not indexes, but are instead files - what is the full file path?

[somesoni2]

Can you see what data is within those indexes?