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9-6 IBM Informix OnLine Database Server Administrator’s Guide
Features Beyond the Scope of OnLine
Distributed Data Queries
The IBM Informix STAR product enables an OnLine user to query and update
more than one database across multiple OnLine database servers within a
single transaction. The OnLine database servers can reside within a single
host machine or on the same network. Support is provided for TCP/IP
networks. For more information about IBM Informix STAR administration,
refer to page 9-15. For more information about using IBM Informix OnLine
within an X/Open environment, refer to the IBM Informix TP/XA User Manual.
Features Beyond the Scope of OnLine
As an OnLine administrator, you need to know the boundaries of OnLine
capabilities. This section describes the tasks that lie outside the scope of the
OnLine database server.
Bad-Sector Mapping
OnLine relies on the operating system of your host machine for bad-sector
mapping. OnLine learns of a bad sector or a bad track when it receives a
failure return code from a system call. When this happens, OnLine retries
several times to ensure that the bad return is accurate and not spurious. If the
bad return is confirmed, OnLine marks as down the chunk where the read or
write was attempted. (Chunk status is D.)
OnLine cannot take any action to identify the bad cylinder, track, or sector
location because the only information available is the byte displacement
within the chunk where the I/O was attempted.
Important: If OnLine detects an I/O error on a chunk that is not mirrored, OnLine
marks the chunk as down. If the down chunk contains logical log files, the physical
log, or the root dbspace, OnLine immediately initiates an abort. Otherwise, OnLine
can continue to operate, but processes cannot write to the down chunk.