TimesTen 应用层数据库缓存学习：16. Aging策略与AWT缓存组

Posted 2020-07-19 dingdingfish

本文讨论如果一个Cache Table设定了Aging策略，那么Aging导致的缓存中数据的删除是否会影响到Oracle数据库?

如果是只读缓存组，当然是不会影响到Oracle的。如果是AWT缓存组，答案也是不会影响，即Aging导致的数据删除不会传播到Oracle，下面通过实验验证一下。

之前的建立缓存组的准备工作此处略过。

在Oracle中建立源表(schema 用户 - tthr)：

create table t1(id int not null, t timestamp not null, primary key(id));

启动cache agent。

建立AWT缓存组(cache管理用户 - cacheadm)，定义Aging策略为基于TimeStamp，生命周期为10秒，检查周期为5秒

CREATE DYNAMIC ASYNCHRONOUS WRITETHROUGH CACHE GROUP "AGEAWT" 
 FROM
  "TTHR"."T1" (
    "ID" NUMBER(38)   NOT NULL,
    "T"  TIMESTAMP(6) NOT NULL,
    PRIMARY KEY("ID")
  )
  AGING USE T LIFETIME 10 seconds CYCLE 5 seconds ON

  start rep agent

在TimesTen中插入数据

$ ttisql "dsn=cachedb1_1122;uid=tthr;pwd=timesten"

Copyright (c) 1996, 2014, Oracle and/or its affiliates. All rights reserved.
Type ? or "help" for help, type "exit" to quit ttIsql.



connect "dsn=cachedb1_1122;uid=tthr;pwd=timesten";
Connection successful: DSN=cachedb1_1122;UID=tthr;DataStore=/home/oracle/TimesTen/tt1122/info/DemoDataStore/cachedb1_1122;DatabaseCharacterSet=AL32UTF8;ConnectionCharacterSet=US7ASCII;DRIVER=/home/oracle/TimesTen/tt1122/lib/libtten.so;PermSize=40;TempSize=32;TypeMode=0;OracleNetServiceName=ttorcl;
(Default setting AutoCommit=1)
Command> select * from t1;
0 rows found.
Command> insert into t1 values(1, sysdate);
1 row inserted.
Command> select * from t1;
< 1, 2016-05-30 01:12:49.000000 >
1 row found.
Command> select * from t1; <- aging生效了
0 rows found.
Command> insert into t1 values(2, sysdate);
1 row inserted.
Command> select * from t1;
< 2, 2016-05-30 01:13:50.000000 >
1 row found.
Command> select * from t1; <- aging生效了
0 rows found.
Command> 

在Oracle中观察数据变化, 可以看到数据不断增加，没有因为Aging而被删除

$ sqlplus tthr/[email protected]

SQL*Plus: Release 11.2.0.2.0 Production on Mon May 30 01:12:27 2016

Copyright (c) 1982, 2010, Oracle.  All rights reserved.


Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> select * from t1;

no rows selected

SQL> select * from t1;

no rows selected

SQL> /

        ID
----------
T
---------------------------------------------------------------------------
         1
30-MAY-16 01.12.49.000000 AM


SQL> /

        ID
----------
T
---------------------------------------------------------------------------
         1
30-MAY-16 01.12.49.000000 AM

         2
30-MAY-16 01.13.50.000000 AM