CFLEVEL and operating system level coexistence
- An operating system release “coexistence” support row of the table with an APAR number indicates
required service in addition to the operating system product code to allow the operating system to
use existing operating system and CF functions, but not exploit new functions that are contained in
a particular CFLEVEL.
- For a given z/OS release / CFLEVEL combination, APARs listed in the corresponding cell and all cells to the left of that cell are required for coexistence.
- A blank area in an operating system coexistence row indicates no additional service is required for the operating system product code to use the CFLEVEL except as noted by the preceding bullet.
- Example: A system at z/OS V2R2 can coexist with a coupling facility up to and including CFLEVEL 21 without additional service, but it requires the service provided by APAR OA52058 to coexist with CFLEVEL 22 and all higher CFLEVELs. Higher CFLEVELs may require additional service as noted in the table. In particular, although there is no service specifically listed for CFLEVEL 23, all APARs listed in corresponding cells to the left of the blank cell are required for coexistence.
- An operating system release “exploitation” support row of the table with text (an ‘X’ or an APAR
number) indicates exploitation of the functions contained in a particular CFLEVEL by the operating
- A blank area in an exploitation row indicates that the z/OS release does not exploit functions provided by that CFLEVEL.
- Example: A system at z/OS V2R2 can exploit all function provided by CFLEVELs up to and including CFLEVEL 20, requires additional service to exploit CFLEVELs 21-24 functions, and cannot exploit functions provided by CFLEVEL 25.
Fix categories (FIXCATs) are used to identify whether an APAR and its related fixing PTF is required by a z/OS system to coexist with a CFLEVEL associated with a hardware server device, or required to exploit function provided by the CFLEVEL. For example, APAR OA56345 is required by the operating system to run with CFLEVEL 24 in a sysplex configuration, whereas OA56774 is required to exploit a particular CFLEVEL 24 function.
See the IBM Fix Category (FIXCAT) values https://www.ibm.com/support/pages/ibm-fix-category-values-and-descriptions that identify fixes that provide z/OS software support for the specific hardware server device associated with the CFLEVEL.
See PR/SM Planning Guide for information on hardware server device model support for CFLEVELs.
- Base coupling facility support
- Structure alter support
- New cache and lock structure functions for improved performance by allowing operations on lists of cache entries (batched registration) and lock entries (batched unlock), rather than on individual entries. These functions were intended for initial exploitation by DB2® and IRLM.
- List monitoring enhancements for keyed list structures (“event monitoring”). The enhancements provide monitoring at a finer level of granularity than was available previously. These functions were intended for initial exploitation by IMS shared message queue.
- Alter and dump support for list structures that use event monitoring.
- User-managed duplexing of DB2 group buffer pools for added availability. This function was intended for initial exploitation by DB2.
- Function that is provided for the TPF operating system. There is no new function for OS/390® exploitation, but all previous CFLEVEL function remains available.
- Cache structure name class queue support that allows entries to be deleted more efficiently. This function was intended for initial exploitation by DB2.
- System-managed rebuild support.
- Support for list structure exploitation by WebSphere® MQ.
- CF-to-CF connectivity support (required for CF Duplexing).
- System-managed duplexing support for all coupling facility structure types.
- Performance enhancements for cache structures by allowing batching of write requests, cross-invalidate requests, and castout requests. These functions were intended for initial exploitation by DB2.
- Performance enhancements for cache structures for IXLCACHE REQUEST=READ_COCLASS requests. This function was intended for initial exploitation by DB2.
- Performance enhancements for coupling facility dispatching and latching.
- Performance enhancements for CF duplexing to suppress RTE signals. Note: This RTE suppression function is not enabled by z/OS.Granular CF CP Utilization reporting by structure.
CF multitasking enhancements (increased number of CF tasks).
- CF duplexing enhancements and shared message queue list notification enhancements.
- Dumping support for CFCC non-disruptive coupling facility. Increased the maximum number of
coupling facility structure instances per coupling facility image from 1023 to 2047 and provided
support for greater than 32 connectors to a coupling facility list or lock structure. Installations
should not deploy more than 32 instances of the application until the following recommendations are
- Upgrade all relevant application instances to a level that supports greater than 32 connectors.
- Ensure that the sysplex contains at least two coupling facilities that are CFLEVEL=17 or higher.
- Functions include:
- Cache performance and reliability improvements.
- Coupling-related adapter interrupt exploitation.
- Enhanced serviceability information for coupling channels.
- Storage-class memory.
- Asynchronous duplexing support.
- Improvements to the efficiency of scheduling and processing work targeted to system-managed
synchronous duplexed CF structures.
To take advantage of this improvement without sacrificing duplexing reliability, you must run z/OS V2R3 or a lower release with a PTF for APAR OA52058 when a CFLEVEL=22 CF is involved in duplexing.New CF structure list monitoring functions include:
- List full/not-full monitoring
- Aggressive list and key range monitoring notification when entries are added to lists and key ranges
- List and key range monitoring notification delays.
The list monitoring functions are available to list structure connectors running on z/OS V2R3 or on z/OS V2R2 with APAR OA51862 when a structure is allocated in a CFLEVEL=22 or higher CF.
- Asynchronous Cache Cross-Invalidation (XI) for Coupling Facility Cache Structures
Asynchronous Cache XI is a communication protocol that notifies connectors of the completion of data invalidation asynchronously with respect to the IXLCACHE request.
The Asynchronous Cache XI function is available to cache structure connectors running on z/OS V2R4 or a lower release with a PTF for APAR OA54688 when a cache structure is allocated in a CF at CFLEVEL 23 or higher.
- CFCC Fair Latch Manager
Provides improvements to the efficiency of scheduling and processing work targeted to system-managed synchronous duplexed coupling facility structures. z/OS must provide new information to the CF to permit exploitation of system-managed synchronous structure duplexing when either structure instance resides in a CF at CFLEVEL 24.
- CFCC Message Path Resiliency Enhancement
When z/OS recognizes an inconsistency in the system identification information associated with a message path to a CF, z/OS will initiate the capturing of diagnostic information from the CF, channel subsystem, and connected z/OS images, and will then take immediate action to transparently correct the inconsistent information dynamically
- Monopolization Avoidance for CF Tasks
A PTF for APAR OA56774, in conjunction with CFCC CFLEVEL 24 provides new function to prevent a runaway sysplex application from monopolizing a disproportionate share of CF resources
- CFCC Fair Latch Manager
- With a PTF for APAR OA60650, in conjunction with CFCC CFLEVEL 25, functions include:
- Read Retry Buffer Extensions
- Read retry buffer support extended to the set of non-idempotent CF cache and lock structure commands, thus reducing the likelihood of encountering indeterminate status results from coupling facility commands.
- Structure Full Threshold
- Allowance for the designation of a percentage of the total number of lock structure record data entries that must remain free after completion of a command to create a record data entry, in order for a creation operation to proceed. To improve connector application resiliency, such as when recovery actions need to allocate structure resources, lock structure connectors can request that the CF reserve a percentage of resources from general mainline application usage until the application explicitly asks for the reserved resources to be used to satisfy structure requests.
- Cache Residency Time Metrics
- Availability of cache structure data and directory residency statistics which indicate how long data area and directory entries reside in a cache structure before they are reclaimed. This information can be used to improve structure sizing and apportionment.
The DISPLAY CF command will always display the actual CFLEVEL of the coupling facility. This might differ from what the application understands to be the operational level of the coupling facility. The operational level refers to the architectural level required to perform the necessary operations against the structure.