TXNGROUPMAX

It is possible to affect the performance of client backup, archive, restore, and retrieve operations by using a larger value for this option:

1. If you increase the value of the TXNGROUPMAX option by a large amount, watch for possible effects on the recovery log. A larger value for the TXNGROUPMAX option can result in increased utilization of the recovery log, as well as an increased length of time for a transaction to commit. If the effects are severe enough, they can lead to problems with operation of the server.
2. Increasing the value of the TXNGROUPMAX option can improve throughput for operations storing data directly to tape, especially when storing a large number of objects. However, a larger value of the TXNGROUPMAX option can also increase the number of objects that must be resent in the case where the transaction is stopped because an input file changed during backup, or because a new storage volume was required. The larger the value of the TXNGROUPMAX option, the more data must be resent.
3. Increasing the TXNGROUPMAX value affects the responsiveness of stopping the operation and the client might have to wait longer for the transaction to finish.

You can override the value of this option for individual client nodes. See the TXNGROUPMAX parameter in REGISTER NODE (Register a node) and UPDATE NODE (Update node attributes).

This option is related to the TXNBYTELIMIT option in the client options file. TXNBYTELIMIT controls the number of bytes, as opposed to the number of objects, that are transferred between transaction commit points. At the completion of transferring an object, the client commits the transaction if the number of bytes transferred during the transaction reaches or exceeds the value of TXNBYTELIMIT, regardless of the number of objects transferred.

The global TXNGROUPMAX option does not apply to object clients. For object clients, the default server global value is 10004.