Progress/400
Product Guide
Local Before-imaging
The DataServer allows you to work with either commitment control on the AS/400 server or local before-imaging on the remote Progress client. Local before-imaging should not replace commitment control on the AS/400. It provides single-user UNDO processing; it does not provide multi-user transaction control. Use it only if commitment control is not in effect for DB2/400 database files. If the client were to fail, you would not be able to undo transactions or recover your database.
NOTE: Commitment control on the AS/400 server and local before-imaging on the client are incompatible. Use only one mechanism.If you do not use journaling on your DB2/400 files, you can use the local before-image file to back out transactions if the remote client continues to run. Progress Software Corporation recommends that you use DB2/400 journaling and commitment control.
By default, the Progress/400 DataServer starts OS/400 commitment control but will open DB2/400 files even if commitment control is not in effect for them. See the "Specifying Transaction Control Techniques" section for instructions on specifying a different response to commitment control.
If the file is opened with commitment control on, the DataServer ends commitment control when the Progress session ends. Opening files with commitment control on assures that standard Progress transaction scoping rules apply. (See the "Transactions" section in "Common Product Information," for information about how the standard Progress RDBMS and OS/400 might view some transactions differently.)
When you use Progress to write to DB2/400 database files that are not journaled, the DataServer writes a message to the OS/400 job log when it opens the nonjournaled file. This is the default behavior for the DataServer, which you can control with the DataServer (-Dsrv TRANSCTL) startup parameter as discussed in the next section.
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