Identifying a Minimum Coupling Facility Level

An application can specify the minimum coupling facility level in which a structure can be allocated. The value of the IXLCONN MINCFLEVEL keyword must be equal to or less than the value specified by the CFLEVEL keyword. If MINCFLEVEL is greater than CFLEVEL, the system rejects the IXLCONN request with reason code IXLRSNCODEBADMINCFLEVEL. The specification of MINCFLEVEL also might prevent an IXLCONN request to connect to an existing structure from completing successfully. If the existing structure is allocated in a coupling facility that is at a lower coupling facility level than the value specified by MINCFLEVEL, the system rejects the IXLCONN request with reason code IXLRSNCODEINSUFFCFLEVELUSER. See Requesting a Minimum CFLEVEL.

The following minimum coupling facility levels support XES functions:

CFLEVEL=1

Maximum of 255 data elements per data item
IXLALTER requests for altering structure size and/or entry-to-element ratio
IXLLIST request types that support entry version number comparison, automatic list key assignment, list cursor manipulation, entry key comparison, and conditional processing based on list authority.

CFLEVEL=2

IXLCACHE REQUEST=REG_NAMELIST
IXLCACHE REQUEST=WRITE_DATA, WHENREG=YES, with VECTORINDEX specified.
IXLLOCK REQUEST=PROCESSMULT for batched release requests.

CFLEVEL=3

IXLLIST request types that support event queues and their use for sublist monitoring. The request types include:
- IXLLIST REQUEST=MONITOR_SUBLIST
- IXLLIST REQUEST=MONITOR_SUBLISTS
- IXLLIST REQUEST=MONITOR_EVENTQ
- IXLLIST REQUEST=READ_EQCONTROLS
- IXLLIST REQUEST=READ_EMCONTROLS
- IXLLIST REQUEST=DEQ_EVENTQ

CFLEVEL=4

IXLALTER requests for altering percentage of list structure storage allocated for event monitor controls.
IXLCACHE REQUEST=UNLOCK_CO_NAME to unlock a single castout lock.
IXLCACHE REQUEST=READ_DATA,RETURNDATA=YES|NO to register interest in an entry without returning the associated data.
IXLCACHE REQUEST=WRITE_DATA, with no data written.
Support for dumping structures that contain event monitor controls.
Performance enhancements to support system cleanup of lock tables for failed connections.

CFLEVEL=5

IXLCACHE functions that include entry version number support, delete type options to control what portions of an entry are to be deleted, suppress registration options to allow an entry to be read or written without registering interest in the entry, and information level options on READ_COCLASS and READ_COSTATS to request additional information to be returned.
IXLCACHE REQUEST=DELETE_NAMELIST command for deleting a specific set of data entries from a structure.
Support for cache structures containing user data field (UDF) order queues.

CFLEVEL=6

No associated support for XES processing.

CFLEVEL=7

Support for the use of a name class mask definition to be assigned to cache entry names. Name classes are used by the coupling facility to assign each entry to a logical group within the structure. Name classes in conjunction with the name class mask definition can be used to improve the processing efficiency of the IXLCACHE REQUEST=DELETE_NAME command.

CFLEVEL=8

Support for the system-managed rebuild process in which the system performs all significant steps in the structure rebuild process with minimal participation by the connectors. Note that it is not necessary to code CFLEVEL=8 if you have coded ALLOWAUTO=YES.
The IXLCSP service, which performs the following types of computations:
- Computes the size and ratios associated with a structure, given structure attributes and object counts
- Calculates structure object counts based on the size, ratios, and other attributes associated with a structure.
Support for user-assigned list entry IDs for list entries created in a list structure.

CFLEVEL=9

Support for three new XES list structure interfaces.
- IXLLSTE — XES List Structure Single Entry Services, which contains all requests that manipulate a single list entry.
- IXLLSTM — XES List Structure Multiple Entry Services, which contains all requests that manipulate multiple list entries.
- IXLLSTC — XES List Structure Control Services, which contains all requests that modify structure controls.
The current XES List Structure Services, IXLLIST, will be maintained for compatibility, but will not be enhanced with new function after OS/390® Version 2 Release 8.
IXLCACHE WRITE_DATA,WHENREG=NO,ASSIGN=YES|NO to allow the suppression of creating a new data entry when an existing data entry is not found.

CFLEVEL=10

No associated support for XES processing.

CFLEVEL=11

Support for the system-managed duplexing rebuild process in which the system performs all significant steps in the structure duplexing rebuild process with minimal participation by the connectors. Note that it is not necessary to code CFLEVEL=11 if you have coded ALLOWAUTO=YES.

CFLEVEL=12

Support for the system-managed duplexing rebuild process in which the system performs all significant steps in the structure duplexing rebuild process with minimal participation by the connectors.

For the most accurate list of CFLEVEL functions with associated hardware and software corequisites, see “CFLEVEL Considerations” at http://www.ibm.com/s390/pso/ on the Library page.