GaussDB T 在线修改redo日志

gaussdb T默认安装的数据库有6组redo日志，每个日志2G，占用太大空间，高斯数据库redo日志的维护与oracle类似，无法不能直接调整大小，可以先添加，再删除。
同时gaussdb维护redo日志还有如下约束：

1. ACTIVE和CURRENT日志不能删除，需要切换日志再删除
2. 最少需要3组redo日志
3. redo日志大小不能小于120M

SQL> select FILE_NAME,BYTES,STATUS,TYPE from DV_LOG_FILES;

FILE_NAME                                  BYTES                STATUS               TYPE                
------------------------------------------ -------------------- -------------------- --------------------
/opt/gaussdb/data/data/log_1               2147483648           INACTIVE             ONLINE              
/opt/gaussdb/data/data/log_2               2147483648           CURRENT              ONLINE              
/opt/gaussdb/data/data/log_3               2147483648           INACTIVE             ONLINE              
/opt/gaussdb/data/data/log_4               2147483648           INACTIVE             ONLINE              
/opt/gaussdb/data/data/log_5               2147483648           INACTIVE             ONLINE              
/opt/gaussdb/data/data/log_0               2147483648           INACTIVE             ONLINE              

6 rows fetched.

开始删除日志，

SQL>  alter database drop logfile ('/opt/gaussdb/data/data/log_0');

Succeed.

SQL> alter database drop logfile ('/opt/gaussdb/data/data/log_1');

Succeed.

SQL> alter database drop logfile ('/opt/gaussdb/data/data/log_2');

GS-00841, Log file is in use, can not be dropped
SQL> alter database drop logfile ('/opt/gaussdb/data/data/log_3');

Succeed.

SQL> alter database drop logfile ('/opt/gaussdb/data/data/log_4');

GS-00812, Database requires at least 3 log files.

从上面报错可以看到，GS-00841：CURRENT状态的日志不能删除，GS-00812：数据库至少需要3个日志文件。

尝试添加3个100m的日志

SQL>  alter database add logfile ('/opt/gaussdb/data/data/log_01' size 100M,'/opt/gaussdb/data/data/log_02' size 100M,'/opt/gaussdb/data/data/log_03' size 100M);

GS-00714, Log file size should be larger than log keep size 125845504
SQL> select 125845504/1024/1024 from dual;

125845504/1024/1024 
--------------------
120.015625          

1 rows fetched.

改为添加三个128M的日志。

SQL> alter database add logfile ('/opt/gaussdb/data/data/log_01' size 128m,'/opt/gaussdb/data/data/log_02' size 128m,'/opt/gaussdb/data/data/log_03' size 128m);

Succeed.

删除剩余的几个日志文件，如果状态仍然是active，需要多切换几次日志，直到inactive即可删除。

SQL> alter database drop logfile ('/opt/gaussdb/data/data/log_4');

Succeed.

SQL> alter database drop logfile ('/opt/gaussdb/data/data/log_5');

Succeed.

SQL> alter system switch logfile;

Succeed.

SQL> select FILE_NAME,BYTES,STATUS,TYPE from DV_LOG_FILES;

FILE_NAME                                                        BYTES                STATUS               TYPE                
---------------------------------------------------------------- -------------------- -------------------- --------------------
/opt/gaussdb/data/data/log_01                                    134217728            UNUSED               ONLINE              
/opt/gaussdb/data/data/log_02                                    134217728            UNUSED               ONLINE              
/opt/gaussdb/data/data/log_2                                     2147483648           ACTIVE               ONLINE              
/opt/gaussdb/data/data/log_03                                    134217728            CURRENT              ONLINE              

4 rows fetched.

SQL>  alter system switch logfile;

Succeed.

SQL> select FILE_NAME,BYTES,STATUS,TYPE from DV_LOG_FILES;

FILE_NAME                                                        BYTES                STATUS               TYPE                
---------------------------------------------------------------- -------------------- -------------------- --------------------
/opt/gaussdb/data/data/log_01                                    134217728            CURRENT              ONLINE              
/opt/gaussdb/data/data/log_02                                    134217728            UNUSED               ONLINE              
/opt/gaussdb/data/data/log_2                                     2147483648           INACTIVE             ONLINE              
/opt/gaussdb/data/data/log_03                                    134217728            ACTIVE               ONLINE              

4 rows fetched.

SQL> alter database drop logfile ('/opt/gaussdb/data/data/log_2');

Succeed.

查看调整后的日志文件：

SQL> select FILE_NAME,BYTES,STATUS,TYPE from DV_LOG_FILES;

FILE_NAME                                                        BYTES                STATUS               TYPE                
---------------------------------------------------------------- -------------------- -------------------- --------------------
/opt/gaussdb/data/data/log_01                                    134217728            CURRENT              ONLINE              
/opt/gaussdb/data/data/log_02                                    134217728            UNUSED               ONLINE              
/opt/gaussdb/data/data/log_03                                    134217728            ACTIVE               ONLINE              

3 rows fetched.

[omm@pr7 data]$ ls -lh log_0*
-rw------- 1 omm dbgrp 128M Jan 31 23:08 log_01
-rw------- 1 omm dbgrp 128M Jan 31 23:06 log_02
-rw------- 1 omm dbgrp 128M Jan 31 23:08 log_03