Record data entries

A record data entry contains information about a resource that is or has been held by a connected user. The information in the record data entry is relevant to the user holding the resource and is normally used by no other user sharing the resource unless the other user needs to use the data to recover for a failure of the resource owner.

Record data entries are 64 bytes long. The first connector to the lock structure specifies whether record data entries are to be used. A record data entry can be allocated within the lock structure when an obtain or an alter request is issued. When a record data entry is allocated in conjunction with an IXLLOCK request, the entry is created with a record data type (RDATATYPE) of zero. See Using the Lock Cleanup and Recovery Service (IXLRT) for information about RDATATYPE.

Each record data entry records information about a connected user's interest in a specific resource. Because record data can persist across system or sysplex outages, if a recovery situation occurs, the users of the lock structure can make use of the record data entries to perform recovery for resources that were held by a user at the time of the failure.

In general, use of a record data entry must be serialized. This is especially important when working with structures in the async duplex established phase. Consider that a record data entry can be read before the update to the secondary structure instance occurs. If both duplexing failover and failure of the connector that made the update occur before the update to the secondary structure instance is made, the read record data entry might not end up in the resultant simplex structure. Also, in cases where a loss of connectivity to the primary structure instance occurs, the request will be redriven to the resultant simplex structure, possibly resulting in a second update to the record data entry. Without proper serialization, another connector could observe that the record data entry was updated multiple times.