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The z/OS zEDC capability is a software-priced feature that is designed to support compression capable hardware. With z15, the zEDC Express (hardware) PCIe feature is replaced by the on-chip compression accelerator unit, but the software (z/OS) component is required to maintain same functionality without increasing CPU costs. 

All data interchange with existing (zEDC) compressed data remains compatible as z15 and zEDC capable machines coexist (accessing same data). Data that is compressed and written with zEDC will be read and decompressed by z15 well into the future. 

The on-chip compression unit has the following operating modes: 

GLYPH<SM590000> Synchronous execution in Problem State, where user application starts instruction in its virtual address space, which provides low latency and high-bandwidth compression/decompression operations). This mod does not require any special hypervisor support, which removes the virtualization layer (sharing the zEDC Express PCIe adapter among LPARs requires virtualization support). 

GLYPH<SM590000> Asynchronous optimization for Large Operations under z/OS. The authorized application (for example, BSAM/QSAM) issues I/O for asynchronous execution and SAP (PU) starts instruction (synchronously as described in the previous paragraph) on behalf of application. The on-chip accelerator enables load balancing of high compression loads and low latency and high bandwidth compared to zEDC Express, while maintaining current user experience on compression. 

Functionality support for the IBM Integrated Accelerator for zEDC is listed in Table 7-3 on page 260 and Table 7-4 on page 262. 

For more information, see Appendix C, “IBM Integrated Accelerator for zEnterprise Data Compression” on page 503. 

## 7.4.3 Coupling and clustering features and functions 

In this section, we describe the coupling and cluster features. 

## Coupling facility and CFCC considerations 

Coupling facility (CF) connectivity to a z15 is supported on the z14, z13, z13s, or another z15. The CFCC levels that are supported on Z servers are listed in Table 7-15. 

<img src='content_image/992130.jpg'>

Consideration:  Because coupling link connectivity with z14 does not support InfiniBand, introducing z15 into an installation requires extra planning. Consider the level of CFCC. For more information, see “Migration considerations” on page 200. 

