Record of an NJS-016 exception for node oracledb

How it happened

Using node oracledb to develop a backend api and encountered NJS-016: buffer is too small for OUT binds exception for a simple select query: select a, b, c from tab@dblink

Debugging

1. Googled NJS-016: buffer is too small for OUT binds and found little help. None of them suits my case.
2. Maybe it has something to do with database link ? Charset for local database is AMERICAN_AMERICA.AL32UTF8 and for remote database is AMERICAN_AMERICA.ZHS16GBK. Changed charset environment variable to the same as remote database, still no luck.
3. Found that column b has some weired behavior: for chinese character value 神经阻滞 it only shows first two characters 神经 when environment variable is set to AMERICAN_AMERICA.AL32UTF8, different from database charset AMERICAN_AMERICA.ZHS16GBK. Column b definition is varchar2(8). Maybe has something to do with this ?

Reasoning

For charset AMERICAN_AMERICA.ZHS16GBK, each chinese character is 2 bytes wide.
For charset AMERICAN_AMERICA.AL32UTF8, each chinese character is 3 bytes wide.
With varchar2(8), it can hold 4 characters on AMERICAN_AMERICA.ZHS16GBK, 2 characters on AMERICAN_AMERICA.AL32UTF8. That’s why it only shows 2 characters when environment variable is AMERICAN_AMERICA.AL32UTF8.
NJS-016 indicates out binds with varhcar2(8) cannot hold 神经阻滞 as it is 4×3=12 bytes wide.

Solution

1. Expand column width from varchar2(8) to a at least varchar2(12)(Intrusive, not recommended).
2. Avoid using database links when charset is different on remote database. Create a distinct connection pool for remote database and execute query on a connection fetched from the pool.