Commands to check for read only Linux file system

Checking for read only on the Linux file system is required when investigating certain DB2  problems especially disk errors

For example, I  saw an error :

--from db2diag.log 
SQL1042C An unexpected system error occurred. SQLSTATE=58004 . 
--from linux logs
Dec 19 08:02:05 server1 kernel: Buffer I/O error on device dm-18, logical block 1562696
Dec 19 08:02:05 server1 kernel: lost page write due to I/O error on dm-18
Dec 19 08:02:05 server1 kernel: SCSI error : <0 0 2 0> return code = 0x20000
Dec 19 08:02:05 server1 kernel: end_request: I/O error, dev sdc, sector 12503752

 

Some root cause analysis highlighted a disk error causing a Linux mountpoint to become a read only.

Commands to check for read only Linux  file system

 

grep ‘ro’ /proc/mounts

--miss remote mounts
grep ' ro ' /proc/mounts | grep -v ':'

 Read More

Linux multipath command

DB2 and Linux IO testing tools

Display Linux CPU information

 

How to check for DB2 Direct IO and FILE SYSTEM CACHING

Question : I’m running DB2 9.5 . How do I check the FILESYSTEM CACHING status on a DB2 tablespace?

 Answer:  DB2 bufferpools and Linux filecache perform approximately the same function.

Thefunction is : copy data from disk.

 DirectIO directs reads from disk into DB2 memory.DirectIO is set up on a tablespace by tablespace basis. The tablespace option is NO FILE SYSTEM CACHING

 Can be applied to: system tablespaces, temporary tablespaces

 Note: LOB and LONG VARCHAR doesn’t benefit – and continues to use file cache

 Check FILESYSTEM caching by  db2 -v "get snapshot for tablespaces on myDB" | more 

Check for File system caching

 

Linux multipath command

Q . How can I see  the details of multipathing on a Red Had Enterprise Linux 5 server, using DM-Multipath?  This is normally a prerequisite for a DB2 installation using SAN and Linux. The DBA can do a quick check

A. Use the multipath   command variations

 

#find the paths to LUN

multipath –l

 #Print multipathed paths showing which devices are multipathed

multipath –v2

 See Also

Storage Monitoring : a quick guide

 

DB2 – Run script on Linux start

A quick method to use for executing a script on Linux  start.

After all the other processes are started by the init command at boot time, the  script is run on Red Hat  based systems:

 

/etc/rc.d/rc.local

 

Add  any extra script\commands references  to this file.

See Also

db2start at start up on Linux

DB2 – db2sysc and instance status

For a quick check on the DB2 instance status on Linux  use:

ps aux | less | grep 'db2sysc'

 

Lists all DB2 instances running on the server.

db2sysc is the main DB2 engine

Related Posts

DB2 health script

Author: Jack Vamvas(http://www.dba-db2.com)