Product Documentation

FairCom ISAM for C

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Create Files

When you create a data file and index, you must specify if that file is to be involved with transaction processing. To get the full benefits, including atomicity and automatic recovery, every file that requires recoverability should have the file mode of ctTRNLOG. Just OR it in with the other file mode values.

Even a library that does not support transaction processing (e.g., standalone multi-user or single-user NO_TRANPROC) can create files that will be transaction ready when opened in a TRANPROC environment. The files automatically revert to NO_TRANPROC when returned to a NO_TRANPROC environment (in which case Begin, Commit, Abort behave as LockISAM calls). To create such a file in a NO_TRANPROC environment simply set the file mode to include either ctTRNLOG or ctPREIMG at create time.

There are two strategies to create a file in a TRANPROC environment that can be used in a NO_TRANPROC environment:

  1. Set the file mode to include either ctTRNLOG or ctPREIMG. After creating the file, but before closing it (which ensures the file is still opened exclusively), call UpdateHeader(filno, TRANMODE, ctXFL_ONhdr) or UpdateHeader(filno, PIMGMODE, ctXFL_ONhdr), respectively. Please be aware that you need to call UpdateHeader() for each physical file just created: data and indexes.
  2. Set the file mode to include either ctTRNLOG or ctPREIMG and including TRANMODE (if ctTRNLOG) or PIMGMODE (if ctPREIMG) in the x8mode member of the extended create block.

An index file that does not include either ctTRNLOG or ctPREIMG in its filemode CANNOT be changed via a call to UpdateHeader(). It must be rebuilt instead.

A call to UpdateFileMode() that changes between ctTRNLOG and ctPREIMG, or ctPREIMG and ctTRNLOG, will have the TRANMODE and PIMGMODE information updated automatically. However, a call to UpdateHeader() to set or turn on TRANMODE or PIMGMODE that is incompatible with the existing file mode or auto switch mode results in a TTYP_ERR (99).

For example, if TRANMODE is already turned on, then PIMGMODE cannot also be turned on. If the file mode is ctPREIMG, TRANMODE cannot be turned on. It is possible to turn off TRANMODE or PIMGMODE by using UpdateHeader() with ctXFLOFFhdr.

A superfile member cannot set TRANMODE or PIMGMODE unless the host has the same settings. UpdateHeader() returns SRCV_ERR (419) if the settings don’t match.

Files can also be created as “Transaction Dependent”, allowing the create to be aborted. See Transaction Dependent Creates and Deletes.