content_image/978564.jpg
<img src='content_image/978564.jpg'>

Workloads can be logically isolated on separate ISM VCHIDs. Alternatively, workloads can be isolated by using VLANs. The ISM VLAN definitions are inherited from the associated IP network (OSA or HiperSockets). 

## Configuration considerations 

The IOCDS (HCD) definitions for ISM PCI VFs are not directly related to the software (SMC-D) use of ISM (that is, the z/OS TCP/IP and SMC-D implementation and usage are not directly related to the I/O definition). 

The user defines a list if ISM FIDs (VFs) in IOCDS (HCD), and z/OS dynamically selects an eligible FID that is based on the required PNet ID. FIDs or VFs are not  defined in Communications Server for z/OS TCP/IP. Instead, z/OS selects an available FID for a specific PNET. Access to more VLANs does not require configuring extra VFs. 

Note:  Consider over-provisioning the I/O definitions; for example, consider defining eight FIDs instead of five. 

For native PCI devices, FIDs must be defined. Each FID in turn also defines a corresponding VF. In terms of operating system administration tasks, the administrator typically references FIDs. VFs (and VF numbers) often are transparent. 

## D.3.9 Software use of ISM 

ISM enables SMC-D, which provides SMC capability within the CPC (SMC without requiring RoCE hardware or network equipment). Host virtual memory is managed by each OS (similar to SMC-R, logically shared memory) following IBM Z PCI I/O translation architecture. 

