Code 4 -- Journal sequence number is at the maximum value.
Means that Sequence number is on maximum level (this is screenshot from MIMIX) :
Best way to generate key pair is to use ssh-keygen utility:
ssh-keygen -t rsa -b 4096
ssh-keygen -t dsa
ssh-keygen -t ecdsa -b 521
ssh-keygen -t ed25519
You can also check actual settings on other files in your libraries.
First run this SQL to collect information about object sizes in all user libraries on your system.
CREATE TABLE YourLibrary.FileName AS (SELECT OBJNAME, OBJLIB,
OBJTYPE, OBJCREATED, OBJSIZE FROM TABLE
(QSYS2.OBJECT_STATISTICS('*ALLUSR','*ALL')) X ) WITH DATA
After this step you can list all files with *MAX4GB ordered by file size.