Data synchronization stage

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Once the system migration to the copy node has completed, IBM® i Migrate While Active using assisted save and restore will enter what is known as the data synchronization stage. During this stage, changes to objects within SYSBAS are tracked using the integrated file system and library tracking lists. These tracking lists are used by Migrate While Active to understand which objects need to be migrated to the copy node.

As depicted in Figure 1, the data synchronization stage is an object-level migration of objects that have changed on the source node after completion of the system migration stage.

Figure 1. Migrate While Active – data synchronization stage
Migrate While Active – data synchronization stage

Data synchronization consists of two parts:

  1. Tracking changes to objects.
  2. Synchronizing changed objects from the source to the copy node.

Migrate While Active includes a hybrid support for tracking changes to objects on the source node.

  1. Changes to Db2® Mirror replication-eligible objects are tracked in the Db2 Mirror object tracking list (OTL).
  2. Changes to non-Db2 Mirror replication-eligible library-based objects are tracked in the library tracking list (LTL). The libraries must reside within SYSBAS.

    The LTL is a list internal to the operating system that maintains information about library-based objects that need to be migrated to the copy node. The current LTL entries can be seen using the LIBRARY_MIGRATION_LIST view or the Db2 Mirror GUI.

  3. Changes to objects in the integrated file system are tracked in the integrated file system tracking list (ITL). The objects must reside within SYSBAS. The tracking does not include objects within /QSYS.LIB or /QDLS.

    The ITL is a list internal to the operating system that maintains information about integrated file system objects that need to be migrated to the copy node. The current ITL entries can be seen using theIFS_MIGRATION_LIST view or the Db2 Mirror GUI.

Some object types that are migrated during the system migration stage are not supported by the data synchronization stage. To see a breakdown of every IBM i object type and the object type’s data synchronization support, refer to Object types and migration.

Migrate While Active also includes a hybrid support of technologies for synchronization of changed objects to the copy node.

  1. Db2 Mirror OTL resynchronization processing is handled by Db2 Mirror replication support. Refer to RESYNC_STATUS view for an explanation of Db2 Mirror resynchronization.
  2. Non-Db2 Mirror replication-eligible library-based objects in SYSBAS that have tracked changes are saved on the source node and restored on the copy node.
  3. Integrated file system objects residing in SYSBAS that have tracked changes are saved on the source node and restored on the copy node.