V9 Update Guide

COMPATIBILITY SYNC_LOG

DEPRECATED

As of FairCom DB Version 9.0, COMPATIBILITY LOG_WRITETHRU is synonymous on both Windows and Unix 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.

Default: OFF

See Also

COMPATIBILITY LOG_WRITETHRU

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.)

Default: OFF

Also See

• COMPATIBILITY DIRECT_IO
• DELAYED_DURABILITY

COMPATIBILITY DIRECT_IO

The FairCom Server for Solaris uses O_DSYNC synchronous writes for the transaction logs when the COMPATIBILITY SYNC_LOG or COMPATIBILITY LOG_WRITETHRU configuration options are specified in the server configuration file.

Furthermore, it is expected the O_DSYNC writes are more efficient than O_SYNC writes. The FairCom Server uses O_DSYNC on systems that define this file open mode and uses O_SYNC on systems that do not define the O_DSYNC file open mode.

COMPATIBILITY DIRECT_IO, is available to revert to the previous behavior of direct I/O.

When the FairCom Server starts up, it writes either the message "Transaction logs using direct I/O." or "Transaction logs using synchronous I/O." to CTSTATUS.FCS to indicate which method of synchronous writes is in use. If neither COMPATIBILITY SYNC_LOG nor COMPATIBILITY LOG_WRITETHRU is specified in ctsrvr.cfg, neither of these messages is written to CTSTATUS.FCS as in that case the server performs asynchronous writes that are flushed by a separate call.

Default: OFF

Also See

COMPATIBILITY LOG_WRITETHRU

COMPATIBILITY SYNC_LOG