HCL Workload Automation, Version 9.4

Setting the synch level parameter

This section describes the impact of the different settings of the synch level parameter in the localopts file. The synch level parameter only impacts UNIX environments.

The I/O activity performed by the HCL Workload Automation engine in managing plans, job streams, and jobs, consists in reading from and writing to the Symphony file and the event files (Mailbox.msg, Intercom.msg, and Courier.msg). When HCL Workload Automation writes to these files it has more than a straightforward write operation to perform. For example, when it writes to the Mailbox.msg file it performs the actions described in the following pseudo code:

TWS_write_event_lock { 
     Lock Mailbox to write 
}

TWS_write_event_update {
     Check Available Space 
     Write Header 
     Write Record 
     Update Write Pointer 
     Unlock Mailbox 
}

Each action requires one or more write accesses to the disk. The way these actions are performed with the different synch level options is as follows:

synch level = high: Each write operation on the event files is immediately physically written to disk. This has a heavy impact on performance caused by the high I/O dependency.
synch level = medium: Each write event is considered as a single operation. For example, while TWS_write_event_lock contains only one action, TWS_write_event_update comprises five actions. With synch level at medium, the five actions in this write event would be completed in one physical disk access, thus drastically reducing the I/O overhead.
synch level = low (default): The operating system decides how and when to synchronize the data to disk. The impact of this option is more difficult to assess, because the rules are different for each operating system and file system.