Connecting to a Structure That Is Being Altered

Structure alter dynamically changes the size and/or entry-to-element ratio of a structure without requiring connectors to quiesce their use of the structure. Connectors must be at the SP 5.2 or higher level, and must have specified ALLOWALTER=YES and CFLEVEL=1 or higher on their IXLCONN invocation. All connectors also must be consistent in their specification for RATIO — if all existing connectors indicated that the entry-to-element ratio can be changed (RATIO=YES) then any new connector must specify RATIO=YES. Assuming that those prerequisites are met, whether a connector is allowed to connect to a structure that is in the process of being altered is determined by the entry and element minimum levels specified on IXLCONN.

IXLCONN accepts a request to connect when the connector specifies:
- ALLOWALTER=YES
- Entry and element minimum levels that are the same or less restrictive than the current composite established for the structure.
The connector must examine the connect answer area to determine the state of the structure.

Note that if the connector determines that the structure is in the duplexing rebuild process as well as a structure alter process, the connector must be able to support the duplexing protocol.
IXLCONN rejects a request to connect with one of the following reason codes:
- IXLRSNCODEALTERNOTALLOW — the connection specified ALLOWALTER=NO.
- IXLRSNCODEALTERRESTRICT
  - The connection specifies more restrictive limits for the entry and element minimum levels than are currently in effect for the structure.
  - The connection specifies RATIO=NO and the current composite established for the structure indicates that the ratio can change during structure alter.
- IXLRSNCODECONNPREVENTED — the connection is not at the SP 5.2 level.

See Altering a Coupling Facility Structure for a description of the alter process.