ttAgingTableLRUConfig

The ttAgingTableLRUConfig procedure sets the Least Recently Used (LRU) aging attributes based on the number of rows per table, giving you control over how many rows delete. You can use it on regular and cache tables defined with an LRU aging policy.

LRU aging enables you to maintain the amount of memory used in a TimesTen database within a specified threshold by deleting the least recently used data. Data is removed if thresholds are reached based on rows for specified tables and on cache instances when applied to specified cache groups. You can limit the number of rows deleted from a specified table by setting row thresholds for the table.

For cache groups, LRU aging is defined at the root table for the entire cache instance. LRU aging can be defined for all cache group types except for explicitly loaded autorefresh cache groups. LRU aging is defined by default on dynamic cache groups. For explicitly loaded cache groups, use time-based aging.

For cache tables, the aging policy is defined on the root table but applies to all tables in the cache group. LRU aging automatically deletes rows from child tables. The aging policy is defined on tables when they are created or altered, using the CREATE TABLE or ALTER TABLE SQL statements.

If both LowRowsThreshold and HighRowsThreshold are set to zero, table based LRU aging is disabled for this table. LRU aging on this table is switched to be based on the permanent memory in use threshold.

Required Privileges

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

Usage in TimesTen Scaleout and TimesTen Classic

This procedure is supported in TimesTen Classic but not supported in TimesTen Scaleout.

Related Views

This procedure has no related views.

Syntax

ttAgingTableLRUConfig(tblOwner, tblName, [LowRowsThreshHold],
[HighRowsThreshHold], [AgingCycle])

Parameters

ttAgingTableLRUConfig has these optional parameters:

Parameter	Type	Description
`tblOwner`	`TT_CHAR (31)`	TimesTen table or cache group owner.
`tblName`	`TT_CHAR (31)`	Name of an application table. Provide the cache root table for a cache group.
`lowRowsThreshold`	`TT_BIGINT`	Sets, displays or resets the number of the rows at which LRU aging is deactivated. LRU aging stops when the number of rows reaches `lowRowsThreshold` rows in the table.
`highRowsThreshold`	`TT_BIGINT`	Sets, displays or resets the number of the rows at which LRU aging is activated. LRU aging starts when the number of rows reaches `highRowsThreshold` rows in the table.
`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, and so on. If the cycle is set to a value of `0`, aging occurs once every second.

Result Set

ttAgingTableLRUConfig returns these results:

Column	Type	Description
`tblOwner`	`TT_CHAR (31) NOT NULL`	TimesTen table or cache group owner.
`tblName`	`TT_CHAR (31) NOT NULL`	Name of an application table or cache root table.
`lowRowsThreshold`	`TT_BIGINT NOT NULL`	The number of the rows at which LRU aging is deactivated.
`highRowsThreshold`	`TT_BIGINT NOT NULL`	The number of the rows at which LRU aging is activated.
`agingCycle`	`TT_INTEGER NOT NULL`	The current setting for the number of minutes between aging cycles, specified in minutes.

Examples

The following example sets the aging threshold for rows in the user1.table1 table to a low threshold of 10K rows and a high threshold of 100K rows. The aging cycle is set to run at the default of once every minute.

Command> Call ttAgingTableLRUConfig('user1', 'table1', 10000, 100000);
< USER1, TABLE1, 10000, 100000, 1 >
1 row found.

The following example sets the aging threshold for rows in the user1.table1 table to a low threshold of 5K rows and a high threshold of 12K rows. The aging cycle is set to run once every two minutes.

Command> Call ttAgingTableLRUConfig('user1', 'table1', 5000, 12000, 2);
< USER1, TABLE1, 10000, 100000, 0 >
1 row found.

The following example turns off aging by setting the low and high thresholds to zero.

Command> Call ttAgingTableLRUConfig('user1', 'table1', 0, 0);
< USER1, TABLE1, 0, 0, 1 >
1 row found.

You can retrieve the threshold settings by running the built-in procedure with just the schema owner and table name.

Command> Call ttAgingTableLRUConfig('user1', 'table1');
< USER1, TABLE1, 10000, 100000, 1 >
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.