The primary performance impact of transaction control is the result of flushing critical data to the transaction logs. Prior to V8.14, the FairCom Server flushed data to the transaction logs by issuing a write to the filesystem cache and then calling a system function to flush filesystem cache buffers to disk. FairCom found the most efficient way to flush data to the transaction logs is to open the logs using a synchronous write mode, in which writes bypass filesystem cache and write directly to disk.
FairCom Server versions 8.14 and later support transaction log write through using the following server configuration options for opening transaction logs in synchronous write mode:
COMPATIBILITY LOG_WRITETHRU is used on Windows systems to instruct FairCom DB to open transaction logs in synchronous write mode. In this mode, writes to the transaction logs go directly to disk (or disk cache), avoiding filesystem cache, so the server avoid the overhead of first writing to the file system cache and then flushing the file system.
COMPATIBILITY LOG_WRITETHRU
Instructs the FairCom Server to open its transaction logs in synchronous write mode. In this mode, writes to the transaction logs go directly to disk (or disk cache), avoiding the file system cache, so the server is able to avoid the overhead of first writing to the file system cache and then flushing the file system. As of FairCom DB Version 9, this is applicable to both Windows and Unix Systems.
Note: On the Solaris operating systems, COMPATIBILITY LOG_WRITETHRU uses the O_DSYNC mode to implement synchronous log writes when available. (Direct I/O with O_SYNC is still used on those systems not supporting O_DSYNC.)
COMPATIBILITY SYNC_LOG is used on Unix systems to instruct the c-tree FairCom DB to open its transaction logs in synchronous write (direct I/O on Solaris) mode. In this mode, writes to the transaction logs go directly to disk (or disk cache), avoiding the file system cache, so the server is able to avoid the overhead of first writing to the file system cache and then flushing the file system cache buffers to disk. This keyword also causes flushed writes for data and index files to use direct I/O. Using this keyword enhances performance of transaction log writes. (This option is deprecated as of V9 and replaced with COMPATIBILITY LOG_WRITETHRU for all platforms.)
On Unix systems, instructs the FairCom DB Server to open its transaction logs in synchronous write (direct I/O on Solaris) mode. In this mode, writes to the transaction logs go directly to disk (or disk cache), avoiding the file system cache, so the server is able to avoid the overhead of first writing to the file system cache and then flushing the file system cache buffers to disk. This keyword also causes flushed writes for data and index files to use direct I/O. Using this keyword enhances performance of transaction log writes.
