|
Problem IC79948
|
Status: Closed |
FAILURE TO ATTACH WHILE ALLOCATING MANY SMALLER SEGMENTS TO SATISFY A LARGE ALLOCATION (> 256GB) |
| product: |
DB2 FOR LUW / DB2FORLUW / 970 - DB2 |
| Problem description: |
This issue impacts Linux systems running SLES 11 and RHEL 6
which use a top-down process address space layout model.
On a Linux AMD64 systems with available RAM > 256GB, DB2 might
attempt creation of a shared memory segment with a size bigger
then 256GB. The allocation fails because of the internal Linux
limitation of the size of the shared memory segment with regular
4k pages.
In cases like that DB2 fails back to creation of many 1GB memory
segments. The attempt of attaching to those segments may fail
with an error in the db2diag.log like the following:
2011-11-11-16.03.22.067021+000 E1756E494 LEVEL: Error
(OS)
PID : 49511 TID : 140737068918528PROC :
db2sysc 0
INSTANCE: db2inst1 NODE : 000 DB :
SAMPLE
APPHDL : 0-7 APPID:
*LOCAL.db2inst1.111111160322
AUTHID : db2inst1
EDUID : 26 EDUNAME: db2agent (SAMPLE) 0
FUNCTION: DB2 UDB, SQO Memory Management,
sqloMemCreateSingleSegment, probe:100
CALLED : OS, -, shmget OSERR: EINVAL
(22)
2011-11-11-16.03.22.072365+000 E2251E781 LEVEL: Severe
PID : 49511 TID : 140737068918528PROC :
db2sysc 0
INSTANCE: db2inst1 NODE : 000 DB :
SAMPLE
APPHDL : 0-7 APPID:
*LOCAL.db2inst1.111111160322
AUTHID : db2inst1
EDUID : 26 EDUNAME: db2agent (SAMPLE) 0
FUNCTION: DB2 UDB, SQO Memory Management,
sqloGetSharedMemoryFromOs, probe:2028
MESSAGE : ZRC=0x850F0005=-2062614523=SQLO_NOSEG
"No Storage Available for allocation"
DIA8305C Memory allocation failure occurred.
DATA #1 : <preformatted>
Unable to attach 387 segments totalling 415434866688 bytes
starting at address
0x0000000000000000. One possible cause may be an improper
setting for the
shmmax Linux kernel tuneable.
2011-11-11-16.03.22.072829+000 E3033E951 LEVEL:
Warning
PID : 49511 TID : 140737068918528PROC :
db2sysc 0
INSTANCE: db2inst1 NODE : 000 DB :
SAMPLE
APPHDL : 0-7 APPID:
*LOCAL.db2inst1.111111160322
AUTHID : db2inst1
EDUID : 26 EDUNAME: db2agent (SAMPLE) 0
FUNCTION: DB2 UDB, base sys utilities,
sqeLocalDatabase::FirstConnect, probe:100
MESSAGE : ZRC=0x850F0005=-2062614523=SQLO_NOSEG
"No Storage Available for allocation"
DIA8305C Memory allocation failure occurred.
DATA #1 : String, 299 bytes
Failed to allocate the desired database shared memory set.
The configured DATABASE_MEMORY plus desired overflow may have
exceeded INSTANCE_MEMORY or the maximum shared memory on the
system.
Attempting to start up with a smaller overflow allowance.
Desired database shared memory set size is (bytes):
DATA #2 : unsigned integer, 8 bytes
415434801152 |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* Users allocating shared memory > 256GB *
****************************************************************
* PROBLEM DESCRIPTION: *
* During memory allocation at database startup, when we fall *
* back to allocating smaller segments, we can fail to attach *
* to one of those segments which will fail the whole *
* allocation. *
****************************************************************
* RECOMMENDATION: *
* Upgrade to DB2 Version 9.7 Fix Pack 6 *
**************************************************************** |
| Local Fix: |
A workaround on SLES 11 / RHEL 6 is to update the Linux kernel
parameter vm.legacy_va_layout=1 prior to issuing db2start. This
will revert to the "bottom-up" address layout used prior to SLES
11 / RHEL 6. In this case multiple segments can be attached
contiguously upwards. Fragmentation can still be an issue,
however (see APAR IC82029) |
| available fix packs: |
DB2 Version 9.7 Fix Pack 6 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 7 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 8 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 9 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 9a for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 10 for Linux, UNIX, and Windows
|
| Solution |
First fixed in DB2 Version 9.7 Fix Pack 6 |
| Workaround |
not known / see Local fix |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 22.11.2011
07.06.2012
07.06.2012 |
| Problem solved at the following versions (IBM BugInfos) |
9.7.FP6
|
| Problem solved according to the fixlist(s) of the following version(s) |
| 9.7.0.6
|
 |
