big undo tablespace

I have Oracle Rac 2 nodes 19c on linux operating system.

my undo tablespace has reached 140GB , i would like if this is normal for very big applications installaed on the same database or this is something strange and it should not grow to this limit, and sometimes the DB shows error cannot extend undo segment so i have to increase the datafile size.

all the datafiles for UNDO tablespace are set to autoextend but the maxsize on them is set to the actual size of the datafile.

my undo retention is 900, and undo management is set to AUTO .

p.s: i have almost 10 applications that are connected to same DB, the DB size is almost 1.5TB