Synchronous delivery - assure_mimix - 10.0

Assure MIMIX Administrator Reference

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Assure MIMIX™ Software
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Assure MIMIX
Assure MIMIX Administrator Reference
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In synchronous delivery mode the target system is updated in real time with journal entries as they are generated by the source applications. The source applications do not continue processing until the journal entries are sent to the target journal.

Each journal entry is first replicated to the target journal receiver in main memory on the target system (1 in Figure 37). When the source system receives notification of the delivery to the target journal receiver, the journal entry is placed in the source journal receiver (2) and the source database is updated (3).

With synchronous delivery, journal entries that have been written to memory on the target system are considered unconfirmed entries until they have been written to auxiliary storage on the source system and confirmation of this is received on the target system (4).

Figure 37.Synchronous mode sequence of activity in the IBM remote journal feature.

Unconfirmed journal entries are entries replicated to a target system but the state of the I/O to auxiliary storage for the same journal entries on the source system is not known. Unconfirmed entries only pertain to remote journals that are maintained synchronously. They are held in the data portion of the target journal receiver. These entries are not processed until confirmation of the I/O for the same entries is received from the source system. Confirmation typically is not immediately sent to the target system for performance reasons.

Once the confirmation is received, the entries are considered confirmed journal entries. Confirmed journal entries are entries that have been replicated to the target system and the I/O to auxiliary storage for the same journal entries on the source system is known to have completed.

With synchronous delivery, the most recent copy of the data is on the target system. If the source system becomes unavailable, you can recover using data from the target system.

In the event that unconfirmed journal entries exist when you need to perform a MIMIX unplanned switch, those journal entries on the source system may be lost and you should contact your MIMIX Services or Support representative for assistance.

Since delivery is synchronous to the application layer, there are application performance and communications bandwidth considerations. There is some performance impact to the application when it is moved from asynchronous mode to synchronous mode for high availability purposes. This impact can be minimized by ensuring efficient data movement. In general, a minimum of a dedicated 100 megabyte ethernet connection is recommended for synchronous remote journaling.