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ABL Essentials
Managing Transactions : Using the UNDO statement : Using the ON phrase on a block header

Using the ON phrase on a block header

In addition to placing one or more UNDO statements within a transaction, you can also specify the default undo processing as part of the block header of a FOR, REPEAT, or DO block. The default action is to retry the block that was undone or, if there is no user interaction that could change the data, to leave the block.
The UNDO phrase as a part of a block header has the same syntax as the UNDO statement itself. You can specify the action to be LEAVE, NEXT, RETRY (with or without a label), or RETURN ERROR or NO-APPLY.
There are four special conditions the AVM recognizes:
*The ERROR condition
*The ENDKEY condition
*The STOP condition
*The QUIT condition