Product Documentation

FairCom ISAM for C

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Transaction File Modes

When you are creating your data files and indexes, you have three options in relation to transaction processing. These options are established by using the appropriate value in the file mode for the file that you are creating.


If you use a file mode of ctTRNLOG, you will get the full benefit of transaction processing, including both atomicity and automatic recovery. If you are not sure of what mode to use, and you do want to use transaction processing, then use this mode.


The ctPREIMG file mode implements transaction processing for a file but does not support automatic file recovery. Files with ctPREIMG mode do not take any space in the system transaction logs.


Transaction controlled indexes with this file mode are recovered more quickly than with the standard transaction processing file mode ctTRNLOG. This feature can significantly reduced recovery times for large indexes and should have minimal effect on the speed of index operations.

ctLOGIDX is only meaningful if the file mode also includes ctTRNLOG. Note that ctLOGIDX is intended for index files only! Do not use ctLOGIDX with data files.

No Transaction Processing

If you do not use either ctPREIMG or ctTRNLOG then the file will not be involved in transaction processing in any way. If you are using transaction processing then you should only do this with files that do not need to be kept as a part of your database. If you are NOT using transaction processing, consider reviewing the ctWRITETHRU file mode in Data and Index Files.

Please note that you should only use one or the other of ctPREIMG and ctTRNLOG.