Large objects (LOBs) in files that are configured for either MIMIX Dynamic Apply or legacy cooperative processing are automatically replicated.
LOBs can greatly increase the amount of data being replicated. As a result, you may see some degradation in your replication activity. The amount of degradation you see is proportionate to the amount of journal entries with LOBs that are applied per hour.
Since the volume of data to be replicated can be very large, you should consider using the minimized journal entry data function along with LOB replication. IBM support for minimized journal entry data can be extremely helpful when database records contain static, very large objects. If minimized journal entry data is enabled, journal entries for database files containing unchanged LOB data may be complete and therefore processed like any other complete journal entry. This can significantly improve performance, throughput, and storage requirements. If minimized journal entry is used with files containing LOBs, keyed replication is not supported. For more information, see Minimized journal entry data.
User exit programs may be affected when journaled LOB data is added to an existing data group. Non-minimized LOB data produces incomplete entries. For incomplete journal entries, two or more entries with duplicate journal sequence numbers and journal codes and types will be provided to the user exit program when the data for the incomplete entry is retrieved and segmented. Programs need to correctly handle these duplicate entries representing the single, original journal entry.
You should also be aware of the following restrictions:
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When using the Compare File Data (CMPFILDTA) command to compare and repair files with LOBs, you must specify a data group when you specify a value other than *NONE for Repair on system (REPAIR).
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Copy Active File (CPYACTF) and Reorganize Active File (RGZACTF) do not work against database files with LOB fields.
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There is no collision detection for LOB data. Most collision detection classes compare the journal entries with the content of the record on the target system.
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Journaled changes cannot be removed for files with LOBs that are replicated by a data group that does not use remote journaling (RJLNK(*NO)). In this scenario, the F-RC entry generated by the IBM command Remove Journaled Changes (RMVJRNCHG) cannot be applied on the target system.