ttAgingLRUConfig

Description

Sets the LRU aging attributes on all regular tables that have been defined with an LRU aging policy. For cache tables, the aging policy is defined on the root table but applies to all tables in the cache group. The aging policy is defined on tables when they are created or altered, using the CREATE TABLE or ALTER TABLE SQL statements.

The LRU aging feature helps applications maintain the usage size of the data store under a specified threshold by removing the least recently used data.

Data is removed if the data store space in-use exceeds the specified threshold values. For cache groups, aging is defined at the root table for the entire cache instance. LRU aging is not allowed for cache groups with AUTOREFRESH. For those cache groups, use time-based aging.

Required privilege

This procedure requires no privilege to query the current values. It requires the ADMIN privilege to change the current values.

Syntax

ttAgingLRUConfig(LowUsageThreshHold, HighUsageThreshHold, AgingCycle)

Parameters

ttAgingLRUConfig has these optional parameters:

Parameter	Type	Description
`lowUsageThreshold`	BINARY_FLOAT	Sets, displays or resets the low end of percentage of data store PermSize, specified in decimals. The bottom of the threshold range in which LRU aging should be deactivated. Default is 80%.
`highUsageThreshold`	BINARY_FLOAT	Sets, displays or resets the high end of percentage of data store PermSize, specified in decimals. The top of the threshold range in which LRU aging should be activated. Default is 90%.
`agingCycle`	TT_INTEGER	Sets, displays or resets the number of minutes between aging cycles, specified in minutes. Default is 1 minute. If you use this procedure to change the aging cycle, the cycle is reset based on the time that this procedure is called. For example, if you call this procedure at 12:00 p.m. and specify a cycle of 15 minutes, aging occurs at 12:15, 12:30, 12:45, etc.

Result set

ttAgingLRUConfig returns these results:

Column	Type	Description
`lowUsageThreshold`	BINARY_FLOAT NOT NULL	The current setting for the low end of percentage of data store PermSize, specified in decimals.
`highUsageThreshold`	BINARY_FLOAT NOT NULL	The current setting for the high end of percentage of data store PermSize, specified in decimals.
`agingCycle`	TT_INTEGER NOT NULL	The current setting for the number of minutes between aging cycles, specified in minutes.

Examples

To set the aging threshold to a low of 75 percent and a high of 95 percent and the aging cycle to 5 minutes, use:

CALL ttAgingLRUConfig (.75, .90, 5);
<.7500000, .9000000, 5>

To display the current LRU aging policy for all tables that defined with an LRU aging policy, call ttAgingLRUConfig without any parameters:

Call ttAgingLRUConfig();

If the tables are defined with the default thresholds and aging cycle, the procedure returns:

<.8000000, .9000000, 1>
1 row found.

To change the low usage threshold to 60%, the aging cycle to 5 minutes and to retain the previous high usage threshold, use:

Call ttAgingLRUConfig (60,,5);
< .6000000, .9000000, 5 >
1 row found.

Note

The values of this procedure are persistent, even across system failures.

If no parameters are supplied, this procedure only returns the current LRU aging attribute settings.