set-ovf-local command

The set-ovf-local command sets and displays the local overflow cache size.

Syntax

set-ovf-local {ws.max}{,fs.max} {(options}

Parameter(s)

Besides displaying the current cache status, set-ovf-local can be used to modify the current cache maximums by specifying the following numeric parameters on the command line:

`ws.max`	Sets the maximum workspace cache size.
`fs.max`	Sets the maximum file space cache size.
`options`	c	Puts a scrub pattern into the local overflow frames.
	f	Flushes all caches. All frames held within the current cache are released back to the main table. Note: This operation is automatically invoked when the maximum values are changed. The act of logging off the system automatically flushes all local overflow caches.
	g	Copies the current maximum cache settings into the global default. Whenever a new user logs on, they automatically acquire this default value. Note: The global defaults are automatically preset to a factory specified value upon reboot, so if a permanent global change is desired, the user should place the set-ovf-local command in the system-coldstart macro.
	s	Suppresses the display.
	x	Disables the local overflow scrubbing.

The presence of a local overflow cache enhances both performance and reliability, and is automatically set up to a reasonable default by the system. Users who want to further tune their overflow usage can use the set-ovf-local command to change this cache to tailor it to specific needs. By default, the checking of local overflow for multiple releases is on. To turn off local overflow checking, remove this line from the system-coldstart macro in dm, and then reboot D3:

set-ovf-local (cgs

When specified without any options, the set-ovf-local command displays the cache status for the current line. The display shows a 2 by 2 grid of numbers.

Legend

`Current`	Current number of frames actually held in a given cache.
`Max`	Maximum number of frames that the cache may hold. Any overflow released to the cache when it has reached its maximum size is deposited directly into the main overflow table.
`WS`	Row showing the current and maximum workspace cache sizes.
`File`	Row showing the current and maximum file cache sizes.

Cache Descriptions

The workspace cache is a generalized cache used for virtually all memory needs. It is automatically set to a default so that simple TCL commands and FlashBASIC programs do not need to access the global overflow table and can thus avoid the performance cost of doing so. If the user is repeatedly using execute statements of more complex programs, then he/she can try boosting the workspace cache size to see if performance improves.

The file cache is used only when update-protection is active. The update-protection scheme deposits frames into this buffer which it guarantees are synchronized so that no other file or workspace on the disk points to it. This virtually eliminates the possibility of so-called doubly linked frame where two files are attached to the same frame after a power outage or crash. This cache should be large enough to cover the largest group or largest pointer item that is protected by the update protection scheme. For example, if the user has a file with 30 KB byte items on a 2 KB frame system, then the file cache should be set to at least 30 KB/2 KB = 15 frames.

Cache Tuning

Ideally, a system should be able to operate out of private overflow caches as much as possible. The less the system accesses the global overflow pool, the greater the system performance, and the less chance there is for the overflow to become corrupted in the event of a power outage. To tune the cache sizes, users can try different cache settings, and run the buffers (s command (For Windows: Not Supported) program to see the change on overflow access. The field ws ovf locks displays the number of system-wide references per second to ws overflow tables. The field file ovf locks displays the number of references to the global overflow table per second.

Warning: All overflow in the local caches will be lost in the event of a power-outage or a system crash. Therefore, the user should be careful not to set the cache settings too high.

Example(s)

Shows that there are currently two workspace frames in the overflow cache with a maximum capacity of 20 frames, and 10 file space frames in the overflow cache with maximum capacity of 30 frames.

set-ovf-local

Private Overflow Cache Status:
         Current      Max
WS       2            20
File     10           30

Sets the maximum workspace cache size for the current line to 100, and the maximum file space cache size to 300.

set-ovf-local 100,300 (s

Releases all frames in the current overflow cache to the global pool.

set-ovf-local (fs

Sets the maximum workspace cache size for the current line to 100, and the maximum file space cache size to 300. The settings are also copied into the global default area. All users logging into the system after this command has been executed will automatically get caches sized to this specification.

set-ovf-local 100,300 (sg