HP OpenView Storage Mirroring User Guide (360226-002, May 2004)

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Auto-Disconnect and Auto-Reconnect
While disk queues are user configurable and can be extensive, they are limited by the amount of physical disk space available.
If the amount of disk space specified for disk queuing is met, additional data could not be added to the queue and data would
be lost. To avoid any data loss, the auto-disconnect and auto-reconnect processes occur.
Exhausted queues on the source—If disk queuing is exhausted on the source, Storage Mirroring will automatically start
disconnecting connections. This is called auto-disconnect. The transaction logs and system memory are flushed allowing
Storage Mirroring to begin processing anew. The auto-reconnect process ensures that any connections that were
auto-disconnected are automatically reconnected. Then, if configured, Storage Mirroring will automatically remirror the data.
This process is called auto-remirror. The remirror re-establishes the target baseline to ensure data integrity, so disabling
auto-remirror is not advised.
Exhausted queues on the target—If disk queuing is exhausted on the target, the target instructs the source to pause. The
source will automatically stop transmitting data to the target and will queue the data changes. When the target recovers, it
will automatically tell the source to resume sending data. If the target does not recover by the time the source queues are
exhausted, the source will auto-disconnect as described above. The transaction logs and system memory from both the source
and target will be flushed then Storage Mirroring will auto-reconnect. If configured, Storage Mirroring will auto-remirror. The
remirror re-establishes the target baseline to ensure data integrity, so disabling auto-remirror is not advised.
Queuing errors—If there are errors during disk queuing on either the source or target, for example, Storage Mirroring cannot
read from or write to the transaction log file, the data integrity cannot be guaranteed. To prevent any loss of data, the source
will auto-disconnect and auto-reconnect. If configured, Storage Mirroring will auto-remirror. The remirror re-establishes the
target baseline to ensure data integrity, so disabling auto-remirror is not advised.
Network socket errors—If there are network socket errors on either the source or target, for example, the TCP/IP
connection is broken for an extended period of time, the TCP/IP timeout set by the operating system has expired, and so on,
the source will auto-disconnect and auto-reconnect. If configured, Storage Mirroring will auto-remirror. The remirror
re-establishes the target baseline to ensure data integrity, so disabling auto-remirror is not advised.