globals contains six comma-separated values that specify how much shared memory to allocate to the database cache for each block size. From left to right, each value is the number of megabytes allocated for:
a – no longer used, always 0
b – no longer used, always 0
c – 8–kilobyte blocks
d – 16–kilobyte blocks
e – 32–kilobyte blocks
f – 64–kilobyte blocks
When all six values are set to 0, the instance automatically allocates 25% of total physical memory. On a 64–bit system, there is a limit of 16 TB.
For more information, see Allocating Memory to the Routine and Database Caches in the “Configuring InterSystems IRIS” chapter in System Administration Guide.
Changing This Parameter
To create a database with a block size other than the default 8–KB blocks, you must enable additional block sizes using the DBSizesAllowed parameter in the [Startup] section.
On the Memory and Startup page of the Management Portal (System Administration > Configuration > System Configuration > Memory and Startup), select the option to Configure Memory Settings Manually. In the Memory Allocated for [block size] Database Cache (MB) field, enter the number of megabytes to allocate for the specified block size.
Instead of using the Management Portal, you can change globals in the Config.config 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).
DBSizesAllowed parameter in the [Startup] section of this reference.
Allocating Memory to the Routine and Database Caches in the “Configuring InterSystems IRIS” chapter in System Administration Guide.
Large Block Size Considerations in the “Configuring InterSystems IRIS” chapter in System Administration Guide.