Re: shared memory - can't backup

33554432
This is the value of shmall.  What do you think?

<posted & mailed>

Joachim Banzhaf wrote:

> Hi Jim,
> 
> You wrote:
> 
>> I am getting this error when I try to run the command 'db2 "backup
>> database dbname online to /opt/BACKUP"' on my 3 databases:
>> SQL1042C  An unexpected system error occurred.  SQLSTATE=58004
>> SQL1084C  Shared memory segments cannot be allocated.  SQLSTATE=57019
>> SQL1084C  Shared memory segments cannot be allocated.  SQLSTATE=57019
>> 
>> I have done some research and my shmmax is set to '1073741824'.
> 
> This is the maximum size of a segment.
> Your problem might be the maximum number of segments is too low.
> 
> extract of "man shmget":
> The followings are limits on shared memory segment resources affecting a
> shmget call:
> 
> SHMALL     System wide maximum of shared memory pages: policy dependent.
> 
> SHMMAX     Maximum size in bytes for a shared memory  segment:
>            implementation  dependent  (currently 4M).
> 
> SHMMIN     Minimum  size  in bytes for a shared memory segment:
>            implementation dependent (currently 1 byte, though PAGE_SIZE is
>            the effective minimum size).
> 
> SHMMNI     System wide maximum number of shared memory segments:
>            implementation dependent  (currently 4096, was 128 before Linux
>            2.3.99).
> 
>> 1) How can I get this to back up?  :)
> 
> Increase SHMMNI/SHMALL parameters and retry.
>   
>> 2) What are my options to move the database to a new server with these
>> problems?
> 
> Maybe shared memory segments got lost somehow: stop instance, use ipclean
> or ipcs/ipcrm to free segs, start instance, if this does not help, reboot.
> 
> Maybe an offline backup works?
>  
> If this all won't work (and noone else has a better idea), you can copy
> the database file by file (with cp, tar, ...).
> You have to consider some things then:
> - This won't work online. Best/easiest to stop the instance before
> copying. - Get the source path with "db2 list db directory" and
>   "db2 get db directory on /path/for/db/from/cmd/above")
> - Don't forget to copy tablespace containers you created outside of the
>   database directory (check with "db2 list tablespaces" and
>   "db2 list tablespace containers for <TBSPACE_ID_from_cmd_above>").
> - Preserve user, group and permissions (e.g. use tar).
> - Recreate exactly the same directory structure (using links is ok if you
>   have another physical disk layout on the new server)
> - Create an instance with the same name, users and groups (with same ID's)
> - Target system should be same/newer db2 version and same/newer fixpak
> level
>   (if newer you might have to migrate the database)
> - Catalog the database on the new server
>   (db2 catalog database xy on /path/from/list/db/cmd/above)
> 
> HTH
> 
> Joachim Banzhaf



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