作者 杨禹航
出品 沃趣技术
PDB Refresh是12C推出的特性,具有对源端PDB进行增量同步的功能,每次刷新会将源端PDB中的任何更改同步到目标PDB(在此环境中目标PDB被称作Refreshable PDB)中,目前增量同步方式有两种:手动方式与自动方式。
一、Refresh MODE语句
在使用Create Pluggable Database创建PDB时指定Refresh MODE子句用来控制是否开启刷新机制。
该子句目前只在"Create Pluggable Database... From"中支持,可以使用此语句指定如下选项:
另外值得一提的是Oracle 18c对Refreshable PDB进行了进一步的增强,增强为Refreshable PDB Switchover(可刷新PDB的切换),在12.2.1中源PDB只能作为源端PDB,而在18c中可对源PDB和目标PDB进行角色转换,该功能类似Active Dataguard的主备切换,只不过Oracle在PDB Refresh中再次实现了该功能。
目前Refreshable PDB只能在只读模式下打开,当Refreshable PDB进行刷新时,Refreshable PDB必须处于关闭状态,只读模式打开时会停止刷新,当再次关闭Refreshable PDB时继续上次的刷新,也可以将Refreshable PDB更改为Refresh MODE NONE模式,更改之后你无法在将PDB改为Refreshable PDB。
另外也可以使用Alter Pluggable Database命令将Refreshable PDB从手动刷新更改为自动刷新,也可以从自动刷新更改为手动刷新,同样通过语句Alter Pluggable Database +Refresh MODE更改为非Refreshable PDB,但是非Refreshable PDB不可以被更改为Refreshable PDB。
同时需要注意的是Refreshable PDB和源PDB必须属于不同的CDB,因此Refreshable PDB需要使用远端的CDB中的PDB来创建,在创建期间必须使用dblink,但实际情况是Source PDB和Refreshable PDB可以属于同一个CDB,只不过在创建Refreshable PDB时必须指定DBlink,DBlink指向自己所在的CDB,否则语法无法通过。
Refreshable PDB的应用场景可以用在开发和测试环境的搭建过程中, 因为数据是采用增量同步的方式,这样就减少了对源数据库的影响,也可以作为online备份库。
Clone源端的PDB前期注意事项:
二、PDB Refreshcesh
如下将源端PDB:woqupdb通过refresh方式克隆到本地,且命名为qdatapdb。
(1)创建目标端到源端库的DBLINK:orcl12c
sys. ora12c>CREATE DATABASE LINK orcl12c CONNECT TO system IDENTIFIEDBY oracle USING 'orcl12c';
Database link created.
Elapsed: 00:00:00.15
sys. ora12c>
克隆源端WOQUPDB
sys. orcl12c>show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
4WOQUPDB READ WRITENO
sys. orcl12c>
(2)目标端配置OMF目录管理方式
sys. ora12c>alter system set db_create_file_dest='/u01/app/oracle/oradata';
System altered.
Elapsed: 00:00:00.04
sys. ora12c>
(3)在目标端使用CREATE PLUGGABLE DATABASE + REFRESH MODE MANUAL语句创建qdatapdb
sys. ora12c>CREATE PLUGGABLE DATABASE qdatapdb FROM woqupdb@orcl12c REFRESH MODE MANUAL;
Pluggable database created.
Elapsed: 00:00:14.20
sys. ora12c>
(4)检查克隆完成的QDATAPDB
sys. ora12c>show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
4 QDATAPDB MOUNTED
sys. ora12c>select pdb_id, pdb_name, status, refresh_mode,refresh_interval from cdb_pdbs;
PDB_ID PDB_NAME STATUS REFRES REFRESH_INTERVAL
---------- ------------------------------ ---------- ----------------------
2 PDB$SEED NORMAL NONE
4 QDATAPDB REFRESHINGMANUAL
Elapsed: 00:00:00.07
sys. ora12c>
通过视图我们可以看到状态为REFRESHING,刷新模式为MANUAL手工刷新。
(5)在源PDB创建表空间tbs1,及测试表t
sys. orcl12c>createtablespace tbs1 datafile size 100M;
Tablespace created.
Elapsed: 00:00:00.30
sys. orcl12c>create user yyh identified by yyh;
User created.
Elapsed: 00:00:00.09
sys. orcl12c>drop user yyh ;
User dropped.
Elapsed: 00:00:01.34
sys. orcl12c>create user yyh default tablespace tbs1 identified by yyh;
User created.
Elapsed: 00:00:00.05
sys. orcl12c>grant dba to yyh;
Grant succeeded.
Elapsed: 00:00:00.04
sys. orcl12c>conn yyh/yyh@woqupdb
Connected.
yyh. woqupdb>createtable t as select * from dba_objects;
Table created.
Elapsed: 00:00:02.18
yyh. woqupdb>selectcount(*) from t;
COUNT(*)
----------
72714
Elapsed: 00:00:00.03
yyh. woqupdb>
(6)在目标端刷新QDatapdb
sys. ora12c>alterpluggable database qdatapdb refresh;
alter pluggable database qdatapdb refresh
*
ERROR at line 1:
ORA-65118: operation affecting a pluggable database cannot be performedfrom another pluggable database
Elapsed: 00:00:00.04
sys. ora12c>conn sys/oracle@qdatapdb as sysdba
Connected.
21:55:00 sys. qdatapdb>set time off
sys. qdatapdb>alterpluggable database qdatapdb refresh;
Pluggable database altered.
Elapsed: 00:00:01.84
sys. qdatapdb>
日志信息:
2018-03-10T21:55:06.187494-05:00
QDATAPDB(4):alter pluggable database qdatapdb refresh
2018-03-10T21:55:06.975492-05:00
Applying media recovery for pdb-4099 from SCN 2800296 to SCN 2802347
Remote log information: count-1
thr-1, seq-5, logfile-/u01/app/oracle/fast_recovery_area/orcl12c/ORCL12C/foreign_archivelog/WOQUPDB/2018_03_10/o1_mf_1_5_1212300924_.arc,los-2791634, nxs-18446744073709551615
QDATAPDB(4):Media Recovery Start
2018-03-10T21:55:06.977285-05:00
QDATAPDB(4):Serial Media Recovery started
2018-03-10T21:55:07.061801-05:00
QDATAPDB(4):Media Recovery Log/u01/app/oracle/fast_recovery_area/orcl12c/ORCL12C/foreign_archivelog/WOQUPDB/2018_03_10/o1_mf_1_5_1212300924_.arc
2018-03-10T21:55:07.503582-05:00
QDATAPDB(4):Successfully added datafile 51 to media recovery
QDATAPDB(4):Datafile #51:'/u01/app/oracle/oradata/ORA12C/671B0AC55A3F2870E0535138A8C0026E/datafile/o1_mf_tbs1_fb96ncby_.dbf'
2018-03-10T21:55:07.998822-05:00
QDATAPDB(4):Incomplete Recovery applied until change 2802347 time 03/10/201821:55:06
2018-03-10T21:55:08.006177-05:00
QDATAPDB(4):Media Recovery Complete (ora12c)
QDATAPDB(4):Completed: alter pluggable database qdatapdb refresh
(7)目标端打开QDatapdb, 检查刷新完成后的数据
sys. qdatapdb>alter database open read only;
Database altered.
Elapsed: 00:00:01.54
sys. qdatapdb>selectcount(*) from yyh.t;
COUNT(*)
----------
72714
Elapsed: 00:00:00.04
sys. qdatapdb>select t.name tablespace_name, d.name from v$tablespacet, v$datafile d where d.ts#=t.ts#;
TABLESPACE_NAME NAME
------------------------------------------------------------------------------------
SYSTEM /u01/app/oracle/oradata/ORA12C/671B/datafile/o1_mf_system_fbjv_.dbf
SYSAUX /u01/app/oracle/oradata/ORA12C/671B/datafile/o1_mf_sysaux_fbk6_.dbf
UNDOTBS1 /u01/app/oracle/oradata/ORA12C/671B/datafile/o1_mf_undotbs1_fbhk7_.dbf
TBS1 /u01/app/oracle/oradata/ORA12C/671B/datafile/o1_mf_tbs1_fbcby_.dbf
Elapsed: 00:00:00.01
sys. qdatapdb>
这里已经刷新完毕,数据同步到本地目标qdatapdb中。
(8)目标库修改为自动刷新模式,每分钟刷新一次
sys. qdatapdb>ALTER PLUGGABLE DATABASE qdatapdb REFRESH MODE EVERY 1 MINUTES;
Pluggable database altered.
Elapsed: 00:00:00.09
sys. qdatapdb>select pdb_id, pdb_name, status, refresh_mode,refresh_interval from cdb_pdbs;
PDB_ID PDB_NAME STATUS REFRES REFRESH_INTERVAL
---------- ------------------------------ ---------- ----------------------
4 QDATAPDB REFRESHING AUTO 1
Elapsed: 00:00:00.05
sys. qdatapdb>
通过视图我们可以看到刷新模式已经被更改为AUTO,间隔时间为1分钟。
(9)源PDB删除测试表
yyh. woqupdb>droptable t;
Table dropped.
Elapsed: 00:00:00.31
yyh. woqupdb>
日志:
2018-03-10T22:01:49.537240-05:00
QDATAPDB(4):ALTER PLUGGABLE DATABASE pdb1 REFRESH MODE EVERY 1 MINUTES
QDATAPDB(4):ORA-65118 signalled during: ALTER PLUGGABLE DATABASE pdb1REFRESH MODE EVERY 1 MINUTES...
2018-03-10T22:02:21.179776-05:00
QDATAPDB(4):ALTER PLUGGABLE DATABASE qdatapdb REFRESH MODE EVERY 1 MINUTES
QDATAPDB(4):Completed: ALTER PLUGGABLE DATABASE qdatapdb REFRESH MODEEVERY 1 MINUTES
2018-03-10T22:02:21.357524-05:00
QDATAPDB(4):alter pluggable database refresh
QDATAPDB(4):Completed: alter pluggable database refresh
2018-03-10T22:03:21.502428-05:00
QDATAPDB(4):alter pluggable database refresh
QDATAPDB(4):Completed: alter pluggable database refresh
2018-03-10T22:04:21.680468-05:00
QDATAPDB(4):alter pluggable database refresh
QDATAPDB(4):Completed: alter pluggable database refresh
通过日志可以观察到目标端每分钟自动刷新一次。
(10)检查目标端数据同步情况
sys. qdatapdb>selectcount(*) from yyh.t;
COUNT(*)
----------
72714
Elapsed: 00:00:00.03
sys. qdatapdb>select open_mode from v$database;
OPEN_MODE
--------------------
READ ONLY
Elapsed: 00:00:00.03
sys. qdatapdb>shutdown immediate
Pluggable Database closed.
sys. qdatapdb>
因目标库在OPEN状态下,虽然日志中显示每分钟刷新,但是数据实际并未正真同步。
(11)1分钟后再次检查数据同步情况
sys. qdatapdb>alter database open read only;
Database altered.
Elapsed: 00:00:01.89
sys. qdatapdb>selectcount(*) from yyh.t;
select count(*) from yyh.t
*
ERROR at line 1:
ORA-00942: table or view does not exist
Elapsed: 00:00:00.01
sys. qdatapdb>
数据已经同步完成。
(12)转换为目标PDB:QDataPDB为非none PDB
sys. ora12c>select pdb_id, pdb_name, status, refresh_mode,refresh_interval from cdb_pdbs;
PDB_ID PDB_NAME STATUS REFRES REFRESH_INTERVAL
---------- ------------------------------ ---------- ----------------------
2 PDB$SEED NORMAL NONE
4 QDATAPDB REFRESHINGAUTO 1
Elapsed: 00:00:00.03
sys. ora12c>alter pluggable database qdatapdb close;
Pluggable database altered.
Elapsed: 00:00:00.19
sys. ora12c>alter session set container=qdatapdb;
Session altered.
Elapsed: 00:00:00.00
sys. qdatapdb>ALTERPLUGGABLE DATABASE qdatapdb REFRESH MODE NONE;
Pluggable database altered.
Elapsed: 00:00:04.01
sys. ora12c>ALTERPLUGGABLE DATABASE qdatapdb REFRESH MODE manual;
ALTER PLUGGABLE DATABASE qdatapdb REFRESH MODE manual
*
ERROR at line 1:
ORA-65261: pluggable database QDATAPDB not enabled for refresh
Elapsed: 00:00:00.00
sys. ora12c>
Note:禁用PDB Refresh功能后,就不能再转换为Refresh PDB。
(13)检查QDataPDB状态
sys. ora12c>conn /as sysdba
Connected.
sys. ora12c>select pdb_id, pdb_name, status, refresh_mode, refresh_intervalfrom cdb_pdbs;
PDB_ID PDB_NAME STATUS REFRES REFRESH_INTERVAL
---------- ------------------------------ ---------- ----------------------
2 PDB$SEED NORMAL NONE
4 QDATAPDB NEW NONE
Elapsed: 00:00:00.00
sys. ora12c>alterpluggable database qdatapdb open;
Pluggable database altered.
Elapsed: 00:00:05.02
sys. ora12c>selectpdb_id, pdb_name, status, refresh_mode, refresh_interval from cdb_pdbs;
PDB_ID PDB_NAME STATUS REFRES REFRESH_INTERVAL
---------- ------------------------------ ---------- ----------------------
2 PDB$SEED NORMAL NONE
4 QDATAPDB NORMAL NONE
Elapsed: 00:00:00.00
sys. ora12c>
QDataPDB的状态已经由自动刷新转换成为了普通的PDB。