n is an integer in the range 256—2,147,483,647 (KB). The default value is -1, which sets the parameter to its maximum value (2,147,483,647 KB).
bbsiz is the maximum memory allocation permitted for a process (in kilobytes). This amount of process private memory is used for symbol table allocation and various other memory requirements, including I/O devices. It is allocated in increasing extents as required by the application until the maximum is reached.
Once this memory is allocated to the process, it is generally not deallocated until the process exits. However, when a large amount of memory is used (for example greater than 32MB) and then freed, InterSystems IRIS® data platform attempts to release deallocated memory back to the operating system where possible.
Changing This Parameter
On the Memory and Startup page of the Management Portal (System Administration > Configuration > System Configuration > Memory and Startup), enter a number of kilobytes in the Maximum Per-Process Memory (KB) row.
Instead of using the Management Portal, you can change bbsiz in the Config.configOpens in a new tab class (as described in the class reference) or by editing the CPF in a text editor (as described in the Editing the Active CPF section of the “Introduction to the Configuration Parameter File” chapter in this book).
When you edit this setting, the updated value applies for all new processes.
When set to the default of -1, or the maximum of about 2 terabytes, maximum size of per process memory is essentially unlimited, as it is very unlikely that a process would approach the use of that much memory.