-
It is an unfortunate coincidence that one of the columns in the table happens to be called “sym”. It could be called anything, but usually it is a symbol column that is used as some kind of key (e.g. instrument ID).
In a splayed table, symbol columns must be enumerated (see Splayed tables | Knowledge Base | kdb+ and q documentation – Kdb+ and q documentation (kx.com)). This is the reason for the sym file at the top level.
You could have multiple sym files in a DB, for example one per table, but all of them need to be in the DB root to work.
code.kx.com
Splayed tables | Knowledge Base | kdb+ and q documentation - Kdb+ and q documentation
Splaying a table stores each column as a separate file, rather than using a single file for the whole table