Db2 分区表坏页的处理

本文仅仅讨论Db2数据库中，当分区表出现坏页，并且数据库能正常连接的情况下，如何处理。

由于是分区表，直接从syscat.tables里查表ID，表空间ID不再适用。在db2diag.log报的obj ID是PARTITIONOBJECTID而非TABLEID，这时候需要查询SYSCAT.DATAPARTITIONS这个视图。

在db2diag.log中遇到以下报错，说明数据页有坏页:

2017-12-23-10.54.39.329394+480 I107589A2588       LEVEL: Severe

PID     : 133323               TID  : 42          PROC : db2sysc 0

INSTANCE: db2inst1             NODE : 000

EDUID   : 42                   EDUNAME: db2pfchr (SAMPLE) 0

FUNCTION: DB2 UDB, buffer pool services, sqlbVerifyCBITS, probe:1110

MESSAGE : ZRC=0x86020019=-2046689255=SQLB_CSUM
"Bad Page, Checksum Error"

          DIA8426C A invalid page checksum was found for page "".

DATA #1 : String, 64 bytes

Error encountered trying to read a page - information follows : 

DATA #2 : String, 95 bytes
CBIT verification error

bitExpected is 1, userByte is 0, sector 24 (from head of page, 0 based)

DATA #3 : Page ID, PD_TYPE_SQLB_PAGE_ID, 4 bytes

59785978

DATA #4 : Object descriptor, PD_TYPE_SQLB_OBJECT_DESC, 72 bytes
    Obj: {pool:6;obj:4;type:0} Parent={6;4}  

下面是一个完整的例子：

1. 创建分区表

db2=> connect to sample

db2=> create tablespace tbs1 managed by automatic storage

db2=> create tablespace tbs2 managed by automatic storage

db2=> create tablespace tbs3 managed by automatic storage

db2=> create table t1(birthdate date) partition by range(birthdate)(partition post80 starting '1980-01-01' ending '1989-12-31' in tbs1,partition post90 starting '1990-01-01' ending '1999-12-31' in tbs2, partition post00 starting
'2000-01-01' ending '2009-12-31' in tbs3)

db2=> insert into t1 values('2003-01-01')

db2=> insert into t1 values('1989-02-02')

db2=> insert into t1 values('1998-02-28')

db2=> insert into t1 values('2007-12-31')

2. 根据pool ID和obj ID找到对应的表和分区

假设db2diag.log中报的错为 Obj: {pool:6;obj:4;type:0} Parent={6;4}

直接查询 syscat.tables 没有结果，说明是个分区表：

inst105@db2a:~> db2 "select substr(tabname, 1, 10) as tabname from syscat.tables where TBSPACEID=6 AND TABLEID=4"

TABNAME

----------

0 record(s) selected.

这时候需要把 syscat.tables 换成 SYSCAT.DATAPARTITIONS, 把TABLEID换成 PARTITIONOBJECTID 来查询：

inst105@db2a:~> db2 "select substr(tabname, 1, 4) as tabname, substr(DATAPARTITIONNAME,1,10) as DATAPARTITIONNAME from SYSCAT.DATAPARTITIONS where TBSPACEID=6 and PARTITIONOBJECTID=4"

TABNAME DATAPARTITIONNAME

-------          -----------------

T1               POST80 <----可以看到，是表T1有坏页，分区为POST80

1 record(s) selected.

inst105@db2a:~> db2 "SELECT TBSPACEID, PARTITIONOBJECTID , DATAPARTITIONID, substr(DATAPARTITIONNAME,1,10) as DATAPARTITIONNAME from SYSCAT.DATAPARTITIONS where tabname='T1'"

TBSPACEID PARTITIONOBJECTID DATAPARTITIONID DATAPARTITIONNAME

-----------        -----------------                 ---------------               -----------------

6                                       4                                 0                    POST80

7                                       4                                 1                    POST90

8                                       4                                 2                    POST00

3 record(s) selected.

3. 使用db2dart DDEL导出对应分区的数据：

inst105@db2a:~$ db2 terminate

DB20000I The TERMINATE command completed successfully.

inst105@db2a:~> db2dart sample /DDEL

Table object data formatting start.

Please enter

Table ID or name, tablespace ID, first page or logical row, num of pages or logical rows:

(may suffix page number with 'p' for pool relative if working with a pool-relative tablespace)
4,6,0,9999999999999 <--这里的4指PARTITIONOBJECTID， 6指TBSPACEID

1 of 1 columns in the table will be dumped.

Column numbers and datatypes of the columns dumped:

0 DATE

Default filename for output data file is SAMPLE_TS6T4.DEL,

do you wish to change filename used? y/n
n

Filename used for output data file is SAMPLE_TS6T4.DEL. If the file exists, the data will be appended to it.

Formatted data being dumped ...

Dumping Page 0 ....

Table object data formatting end.

The requested DB2DART processing has completed successfully!

Complete DB2DART report found in: SAMPLE.RPT

inst105@db2a:~> cat SAMPLE_TS6T4.DEL

19890202

inst105@db2a:~>

如果是db2 9.7版本的，导出的数据默认是放在db2dump/DARTXXXX目录下的

4. 使用db2dart MT选项将对应分区标记为无效

inst105@db2a:~$ db2dart sample /MT

Please enter Table ID or name, tablespace ID, and password:
4,6,XLQIXMNG <--分别输入表空间ID，PARTITIONOBJECTID和服务密码（服务密码有效期7天，需要向IBM申请）

Mark table phase start.

Set drop-pending (unavailable) state for table objects.

Set state for DAT object 4 tablespace 6.

Modification for page (obj rel 0, pool rel 128) of pool ID (6) obj ID (4), written out to disk successfully.

Modification written out successfully.

Mark table phase end.

The requested DB2DART processing has completed successfully!

Complete DB2DART report found in: SAMPLE.RPT

inst105@db2a:~>

5. detach并删除对应分区

inst105@db2a:~$ db2 connect to sample

inst105@db2a:~$ db2 "select * from t1"

BIRTHDATE

----------

SQL1477N For table "INST105.T1" an object "4" in table space "6" cannot be

accessed. SQLSTATE=55019

inst105@db2a:~$ db2 "alter table t1 DETACH PARTITION POST80 into temp"
<--把这个分区detach出去之后，表T1即可恢复访问

DB20000I The SQL command completed successfully.

inst105@db2a:~$ db2 "select * from t1"

BIRTHDATE

----------

02/28/1998

01/01/2003

12/31/2007

3 record(s) selected.

inst105@db2a:~> db2 "drop table temp"

DB20000I The SQL command completed successfully.

6. 根据第三步中导出的数据，可以新建一个表，导入数据之后，再attach到t1上