ZFString is an integer in the range 0—32,767. The default is 0.
ZFSize is an integer in the range 0—270,336 (bytes). The default is 0.
zfheap contains two comma-separated values which configure the $ZF heap: ZFString and ZFSize. For more details about the $ZF heap, see the chapter “Creating a Callout Library” in Using the Callout Gateway.
This zfheap parameter is the number of characters InterSystems IRIS® data platform allows for a single string parameter on the $ZF heap. How many bytes this actually requires depends on whether you are using Unicode (2-byte characters) or 1-byte characters on UNIX®. When set to 0, InterSystems IRIS automatically uses the system default value for ZFString, which is 32,767.
This zfheap parameter is the number of bytes InterSystems IRIS® data platform allocates for the $ZF heap for all purposes. The $ZF heap consists of the total number of bytes allocated in virtual memory for all $ZF input and output parameters, including the space for strings allowed by the first value. When set to 0, InterSystems IRIS automatically calculates an appropriate value for ZFSize, based on the value of ZFString. The formula is as follows:
ZFSize = (BytesPerCharacter * ZFString) + 2050
Using the default value for ZFString, which is 32,767:
If you are using Unicode, a single character is 2 bytes. The calculated value for ZFSize is then 67584 (or 2 * 32767 + 2050) bytes.
On UNIX®, a single character is 4 bytes. The calculated value for ZFSize is then 133118 (or 4 * 32767 + 2050) bytes.
Changing This Parameter
On the Advanced Memory page of the Management Portal (System Administration > Configuration > Additional Settings > Advanced Memory), edit the values for ZFString or ZFSize. InterSystems recommends that this parameter be set to 0,0.
Instead of using the Management Portal, you can change zfheap 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).
If you edit this setting, you must restart InterSystems IRIS to apply the change.