Sys in kingbasees_ Checksums bad block detection function

keyword ：

KingbaseES ,checksum, Bad block detection

1. sys_checksums brief introduction

sys_checksums Used to detect kingbase Bad block condition of data stored on disk , It can also be used to start data checksum and close data checksum .

Turn on checksum after ,kingbase Take data from shared buffer Write to disk , The checksum; Read from disk block To shared buffer in , It will also be calculated block Of checksum, Contrast exists page The head of the checksum Is it consistent . stay shared buffer Inside block, Read 、 There is no need to calculate when updating checksum.

2. sys_checksums Practice

2.1）./sys_ctl –D ./data stop Stop database , Check whether the database is enabled checksum

./sys_checksums –c ./data

2.2） Enable checksum

./sys_checksums -e ./data

2.3）./sys_ctl -D ./data start Start database ,ksql Connect to database , Create table

2.4） perform select * from sys_relation_filepath('t1'); Query table t1 Corresponding physical file

2.5） Stop database

2.6） Use vim -b ./data/base/16078/16396 Open physical file , Then enter... In command mode :%!xxd, Modify block content , After modification , Command line mode input :%!xxd -r Restore binary format , Save and exit （ The following figure is modified 7400 by 7300）

2.7） Use ./sys_checksums -c ./data Detect bad block