What is the maximum size that -B or -B2 can be set for a database?

The limit for -B1 and -B2 is documented as: 

 

The maximum value of the sum of -B + -B2: 1,000,000,000 for 64-bit platforms; 125,000,000 for 32-bit platforms.
The maximum is system dependent and limited by available memory. 

 

Note:  

On the AIX platform, when starting a database with large shared memory requirements (for instance, when the -B exceeds the allotted system paging space), the system may become unstable if the PSALLOC=early environment variable is not set.