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.

CHGMSGD MSGID(CPI6705) MSGF(ADMSYS/QCPFMSG) FMT((*CHAR 17) (*CHAR 10) 
(*CHAR 6) (*CHAR 10) (*UBIN 8) (*CHAR 10) (*CHAR 6) (*CHAR 10) (*DTS) (*DTS) (*ITV))