Data integrity and IFI

Although IFI displays Db2 statistics, agent status, and resource status data, it does not change or display Db2 database data.

When a process retrieves data, information is moved from Db2 fetch-protected storage to the user's address space, or from the address space to Db2 storage, in the storage key of the requester. Data that is moved by the READA request is serialized so that only clean data is moved to the address space of the requester.

The serialization techniques used to obtain data for a given READA request might minimally degrade performance on processes that simultaneously store data into the instrumentation facility buffer. Failures during the serialization process are handled by Db2.

The Db2 structures that are searched on a READS request are validated before they are used. If the Db2 structures are updated while being searched, inconsistent data might be returned. If the structures are deleted while being searched, users might access invalid storage areas, causing an abend. If an abend does occur, the functional recovery routine of the instrumentation facility traps the abend and returns information about it to the application program's IFCA.