The Answer to Free Memory, Swap, Oracle and everything

1
The Answer to Free Memory, Swap, Oracle and
everything
A presentation about using memory where its
needed most
Christo Kutrovsky The Pythian Group 2007 April
2
The Answer to Free Memory, Swap, Oracle and
everything
The 45 minutes version
A presentation about using memory where its
needed most
Christo Kutrovsky The Pythian Group 2007 April
3
Who Am I?

• Joined Pythian in 2003
• Became team lead for one of Pythian's service
  delivery teams in 2006
• Notable clients Palm Coast Data, Freshdirect.com
• Presented at Collaborate '06, '07, RMOUG
• Special interest in 11g, RAC, Disk IO
  performance, and memory
• Pythian's delegate to the 11g beta, participated
  at the camp level (two visits)

4
Who is Pythian?

• Provides turnkey global data architecture and
  operations teams on a linear-cost-to-effort basis
• Founded in 1997, headquartered in Ottawa, Canada,
  with offices in India and Australia
• Supporting almost 100 clients worldwide and more
  than 600 production databases
• Almost 50 production engineers engaged in client
  service delivery
• Broad data infrastructure expertise primarily
  focused on Oracle, Microsoft SQL Server, and
  MySQL on enterprise hardware

5
Agenda

• Types of memory
• Virtual Memory areas
• How do we monitor memory usage
• And make sense of it
• Oracle examples
• Case studies

6
Questions

• How many developers
• How many managing linux
• How many managing unix (AIX, solaris)
• How many have root access
• How many have control of database memory
  consumption

7
Terminology

• What is memory
• The ability of a computer system to store data

8
Types of Memory

• Short term
• RAM (memory)
• Long term (permament)
• Disk, tape (storage)

9
Types of Memory - physical

• CPU Registers
• fastest, very limited
• CPU Cache (L1/L2/L3)
• some latency, LRU maintained
• RAM
• major latency (relatively), partially LRU
• Disk
• do something else while you wait

10
What is RAM

• Faster, temporary storage
• A work area
• A place where you put your data while you process
  it

11
The Many caches
CPU Registers2 ns
CPU Cache 8 ns 14
Main Memory (RAM) 100ns 112
CPU
Disk Long term memory 3000000 ns 130000
TAPE even longer
12
CPU Cache CPU Registers

• CPU Registers your two hands (or more)
• You use them to hold the items while you work on
  them
• CPU Cache your desk
• You use it as a quickly accessible location to
  store your most used items
• Represents your current tasks

13
Main Memory - RAM

• RAM Random Access Memory
• Its like your office
• Need to get up from your desk to grab items to
  work on
• You usually grab multiple at a time to save
  roundtrips

14
Our office
Your hands2 seconds
CPU Cache Desk4 sec.
Main Memory (RAM) Your office 12 seconds
CPU
Disk Flying to Australia 8 hours
TAPE use a cargo ship to go
15
Growing your office

• You always need more
• Your office needs to handle all your active
  clients, or they will be unhappy
• Running out of space in your office is not
  acceptable

16
The Disk extending the memory

• The Solution?
• Ship some of your least needed binders to
  Australia
• Relatively complex process
• need to find the least needed binders
• need to know how to return them, when they are
  needed

17
Introduction to virtual memory

• Processes see memory independently, as if it
  was alone on the system
• Each process has freedom to use addresses in the
  whole user address space
• Typically 3 Gb user space, 1 Gb system space
  (on 32 bit)

18
Virtual memory mapping
32 bit addressing space
0 gb
1 gb
2 gb
3 gb
4 gb
P1
P2
Reservedvirtualregion for the system(kernel)
RAM
RAM split into 4 kb chunks
19
VM Management

• Implemented via per process page table
• Indicates
• page location (disk/memory)
• page permissions (read/write/execute)
• page attributes (ex. copy on write)

20
Virtual memory PTE table
PTE Table for P1
rw in RAM 0xFFA
rw in RAM 0xFFB
RAM
in RAM 0xFFC copy on write
w unallocated
rw on disk - SWAP
rx on disk - FILE
unallocated
FILE
SWAP
P1
21
Additional benefits from VM

• Protection
• Features
• memory mapped files
• in memory file system
• shared memory
• shared memory copy on write
• Use more then what you have

22
Concept types of memory

• Shared
• initially exists on disk
• file cache(linux), buffers, system cache
• initially does not exist on disk
• anonymous(linux), computed(aix)
• Private
• does not exist on disk
• special case copy on write

23
Linux VM Components

• direct user dependant types of memory
• Buffers (shared)
• Cached (shared)
• Anonymous (private or shared)
• Hugepages
• indirect (system) managed areas
• Slab kernel structures
• PageTables

24
VM areas with Oracle
System
User
SLAB
Buffers
Mapped
Anonymous (PGA,PLSQL arrays)
Pagetables
Cached
IPC Memory (SGA)
25
Monitoring

• Monitoring Memory
• with Oracle in mind

26
TOP

• top
• most commonly used tool
• most confused interpretation

27
top sample output

• top - 220311 up 319, 2 users, load average
  2.98, 1.22, 0.52
• Tasks 89 total, 1 running, 88 sleeping, 0
  stopped, 0 zombie
• Cpu0 0.7 us, 0.8 sy, 0.0 ni, 0.3 id,
  98.0 wa, 0.2 hi, 0.0 si
• Cpu1 0.0 us, 0.8 sy, 0.0 ni, 97.6 id,
  1.4 wa, 0.2 hi, 0.0 si
• Cpu2 0.0 us, 0.2 sy, 0.0 ni, 99.7 id,
  0.2 wa, 0.0 hi, 0.0 si
• Cpu3 0.2 us, 0.2 sy, 0.0 ni, 33.6 id,
  66.1 wa, 0.0 hi, 0.0 si
• Mem 8310308k total, 8049068k used, 261240k
  free, 36620k buffers
• Swap 7823644k total, 572k used, 7823072k
  free, 3395900k cached
• PID USER PR NI VIRT RES SHR S CPU
  MEM TIME COMMAND
  
• 8494 oracle 16 0 1662m 1.6g 1.5g D 2.0
  19.8 003.15 oracletest (LOCALYES)
• 4796 oracle 16 0 1626m 1.5g 1.5g S 1.0
  19.5 003.91 ora_dbw1_test
  
• 4794 oracle 15 0 1626m 1.5g 1.5g S 0.7
  19.5 012.23 ora_dbw0_test
  
• 4798 oracle 16 0 1626m 1.5g 1.5g S 0.7
  19.5 003.97 ora_dbw2_test
  
• 4800 oracle 16 0 1626m 1.5g 1.5g S 0.7
  19.5 004.09 ora_dbw3_test
  
• 1 root 16 0 2384 600 512 S 0.0
  0.0 000.86 init 3
  
• 2 root RT 0 0 0 0 S 0.0
  0.0 000.00 migration/0
  
• 3 root 34 19 0 0 0 S 0.0
  0.0 000.00 ksoftirqd/0

28
Top data comes from

• /proc/ltpidgt/status
• cat /proc/10450/status
• Name oracle
• State S (sleeping)
• SleepAVG 98
• Tgid 10450
• Pid 10450
• PPid 1
• TracerPid 0
• Uid 503 503 503 503
• Gid 503 503 503 503
• FDSize 256
• Groups 503 603

VmSize 83424 kB VmLck 0 kB VmRSS
1484204 kB VmData 1612 kB VmStk 124
kB VmExe 52720 kB VmLib 8420 kB
29
top additional columns

• top can have additional columns
• swap file usage
• computed
• code
• data
• THEY ARE ALL WRONG

30
vmstat

• vmstat 2
• procs -----------memory---------- ---swap--
  -----io---- --system-- ----cpu----
• r b swpd free buff cache si so bi
  bo in cs us sy id wa
• 0 0 0 3631424 11096 120204 0 0
  35 31 255 20 0 0 99 0
• 0 0 0 3631488 11096 120204 0 0
  0 0 1014 18 0 0 100 0
• 0 0 0 3631488 11096 120204 0 0
  0 0 1012 16 0 0 100 0
• r run queue how many processes currently
  waiting for or running on the CPU
• b how many processes waiting, usually waiting
  on IO
• swpd swap memory usage
• free free memory
• cache file system cache

31
vmstat cont

• vmstat 2
• procs -----------memory---------- ---swap--
  -----io---- --system-- ----cpu----
• r b swpd free buff cache si so bi
  bo in cs us sy id wa
• 0 0 0 3631424 11096 120204 0 0
  35 31 255 20 0 0 99 0
• 0 0 0 3631488 11096 120204 0 0
  0 0 1014 18 0 0 100 0
• 0 0 0 3631488 11096 120204 0 0
  0 0 1012 16 0 0 100 0
• si/so swap in / out in Kb/sec
• bi/bo bytes in / out in Kb/sec
• cs context switches
• us/sy/id/wa user/system/idle/wait time for CPUs

32
/proc/meminfo

• cat /proc/meminfo
• MemTotal 8310308 kB
• MemFree 93448 kB
• Buffers 132036 kB
• Cached 3413324 kB
• SwapCached 0 kB
• Active 1658252 kB
• Inactive 1942032 kB
• HighTotal 7470528 kB
• HighFree 8768 kB
• LowTotal 839780 kB
• LowFree 84680 kB

SwapTotal 7823644 kB SwapFree 7823072
kB Dirty 100 kB Writeback
0 kB Mapped 82500 kB Slab
92028 kB Committed_AS 490700 kB PageTables
3952 kB VmallocTotal 106488 kB VmallocUsed
5964 kB VmallocChunk 99900
kB HugePages_Total 2200 HugePages_Free
1088 Hugepagesize 2048 kB
33
/proc/meminfo 64 bit
SwapTotal 4816888 kB SwapFree 4192148
kB Dirty 252 kB Writeback
0 kB Mapped 1350480 kB Slab
461584 kB CommitLimit 6851404 kB Committed_AS
4959776 kB PageTables 46668
kB VmallocTotal 536870911 kB VmallocUsed
2992 kB VmallocChunk 536867847
kB HugePages_Total 2000 HugePages_Free
128 Hugepagesize 2048 kB

• cat /proc/meminfo
• MemTotal 8165032 kB
• MemFree 106428 kB
• Buffers 219484 kB
• Cached 2864760 kB
• SwapCached 69256 kB
• Active 1508428 kB
• Inactive 1915392 kB
• HighTotal 0 kB
• HighFree 0 kB
• LowTotal 8165032 kB
• LowFree 106428 kB

34
MemTotal

• Total memory visible by the OS
• If its not what youve put in the machine,
  probably you have a bad SIM/DIMM

35
MemFree

• Memory that is currently un-occupied and
  available to use immediately
• Not the maximum amount of memory available at the
  moment
• Controlled by (Linux RH4) /proc/sys/vm/min_free_kb
  ytes

36
MemFree example

• grep MemFree /proc/meminfo
• MemFree 26568 kB
• echo 900000 gt /proc/sys/vm/min_free_kbytes
• grep MemFree /proc/meminfo
• MemFree 210056 kB

37
Buffers

• Cache of raw disk blocks
• Usually occupied with ext3 metadata
• Mostly ext3 pointers (extent management)
• Not the cache of actual user data
• In older kernels, was controllable

38
Cached

• File system cache
• If direct IO is not used for datafiles will
  have your datafiles cached
• Binary (for execution) memory
• includes the oracle binary caching
• all the libraries caching
• Does not mean occupied usually can be
  released immediately
• The Oracle SGA when not using hugepages

39
Cached example part 1

• root_at_ cat /proc/meminfo
• MemFree 8232512 kB
• Buffers 9328 kB
• Cached 28372 kB
• du -smc indx01_
• 1714 indx01_01.dbf
• 1761 indx01_02.dbf
• 1722 indx01_03.dbf
• 5197 total
• cat indx01_ gt /dev/null

40
Cached example part 2

• root_at_ vmstat 2
• procs -----------memory---------- ---swap--
  -----io---- --system-- ----cpu----
• r b swpd free buff cache si so bi
  bo in cs us sy id wa
• 0 0 0 8093888 10808 163392 0 0
  0 0 1012 17 0 0 100 0
• 0 0 0 8093952 10808 163392 0 0
  0 0 1012 16 0 0 100 0
• 0 1 0 7956736 10948 300272 0 0
  68602 0 1567 1126 0 2 76 22
• 0 1 0 7808576 11092 448068 0 0
  73992 80 1623 1210 0 2 75 23
• 0 1 0 2847616 16104 5397616 0 0
  65792 0 1542 1076 0 2 75 23
• 0 0 0 2766272 16180 5479180 0 0
  40698 0 1341 675 0 1 85 14
• 0 0 0 2766208 16192 5479168 0 0
  0 114 1033 22 0 0 100 0
• cat /proc/meminfo
• MemFree 2766464 kB
• Buffers 16192 kB
• Cached 5479168 kB

41
Cached example 2 part 1

• cat indx01_ gtnewfile
• vmstat 2
• procs -----------memory---------- ---swap--
  -----io---- --system-- ----cpu----
• r b swpd free buff cache si so bi
  bo in cs us sy id wa
• 0 0 0 2765312 17044 5479356 0 0
  0 0 1012 17 0 0 100 0
• 0 3 0 2405376 17428 5833612 0 0
  16 36866 1324 144 1 18 76 6
• 0 2 0 2143616 17688 6091532 0 0
  4 111748 2000 213 0 16 50 34
• 0 1 0 16832 6784 8198556 0 0
  8556 26684 1942 1267 0 2 74 24
• 1 1 0 16832 6856 8198744 0 0
  12518 20720 2130 1767 0 3 74 23
• cat /proc/meminfo
• MemFree 16768 kB
• Buffers 2192 kB
• Cached 8196908 kB
• Dirty 277468 kB
• Writeback 0 kB

42
Cached example 2 part 2

• cat /proc/meminfo
• MemFree 20672 kB
• Buffers 3300 kB
• Cached 8191900 kB
• Dirty 0 kB
• Writeback 0 kB
• rm newfile
• procs -----------memory---------- ---swap--
  -----io---- --system-- ----cpu----
• r b swpd free buff cache si so bi
  bo in cs us sy id wa
• 0 0 0 23296 3380 8189480 0 0
  0 28 1015 18 0 0 100 0
• 0 1 0 3257472 3948 4996372 0 0
  284 0 1084 160 0 14 78 8
• 0 1 0 3255552 5828 4996572 0 0
  940 0 1247 485 0 1 75 24
• 0 1 0 3253696 7616 4996344 0 0
  884 96 1237 470 0 2 75 23
• 0 0 0 3253440 7988 4996492 0 0
  186 0 1061 112 0 0 95 4
• 0 0 0 3253440 7988 4996492 0 0
  0 0 1012 14 0 0 100 0

43
Swap

• SwapTotal
• SwapFree
• SwapCached
• written to swap, but still in memory
• applies only to anonymous memory
• OS will anticipate memory needs, and pre-swap
  inactive data, but keep it in memory
• Actual swapping (memory that will need to be read
  from disk) SwapTotal - SwapFree - SwapCached

44
Active/Inactive

• Active recently used memory
• Includes all types of memory (cached, buffers,
  anonymous)
• OS will try to keep it in RAM
• Inactive memory that will be first reused
• free memory
• Can be used to gauge the working set

45
High/Low Total/Free

• 32 bit limitations, no high memory on 64 bit
• Some kernel structures cannot be allocated in
  high memory
• Used to be a problem in older kernels, newer
  kernels protect low memory

46
Dirty Writeback

• Dirty cache/buffers memory that requires to be
  written to disk
• thresholds can be adjusted
• Writeback memory actively been written to disk
• Can reach high values with async writes with
  large queue

47
Committed_AS Mapped

• Committed_AS
• Total memory requested on the system
• Not used, just requested
• If every process in the system is to touch and
  use the memory it has requested, this is how much
  would be used
• Mapped
• memory used for in-memory mapped files
• all anonymous memory
• includes committed touched memory

48
Committed_AS - example

• cat grab.c
• main() void p
• pmalloc(1073741824)
• sleep(60)
• cat /proc/meminfo
• ...
• MemFree 3230592 kB
• ...
• Committed_AS 49972 kB
• ./grab
• cat /proc/meminfo
• ...
• MemFree 3230464 kB
• ...
• Committed_AS 1098808 kB

49
Slab

• Slab in-kernel data structures cache
• similar to Oracles shared_pool
• designed to prevent memory fragmentation
• detailed monitoring/proc/slabinfoslabtop
• Basically system space

50
slabtop ordered by cache size

• Active / Total Objects ( used) 88874 /
  139343 (63.8)
• Active / Total Slabs ( used) 5839 / 5846
  (99.9)
• Active / Total Caches ( used) 90 / 132
  (68.2)
• Active / Total Size ( used) 17286.03K /
  23311.27K (74.2)
• Minimum / Average / Maximum Object 0.01K /
  0.17K / 128.00K
• OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE
  SIZE NAME
• 32382 24900 76 0.27K 2313 14
  9252K radix_tree_node
• 56925 40013 70 0.05K 759 75
  3036K buffer_head
• 364 363 99 4.00K 364 1
  1456K size-4096
• 2485 2471 99 0.54K 355 7
  1420K ext3_inode_cache
• 2376 413 17 0.50K 297 8
  1188K size-512
• 256 256 100 3.00K 128 2
  1024K biovec-(256)
• 4576 4481 97 0.15K 176 26
  704K dentry_cache
• 10248 4548 44 0.06K 168 61
  672K size-64
• 4340 1215 27 0.12K 140 31
  560K size-128
• 1980 316 15 0.25K 132 15
  528K size-256

51
HugePages

• 2Mb pages
• organized in a separate memory pool
• locked in memory
• available only to shared memory requests
• pre-allocated via kernel parameter

52
Shared memory mapping
32 bit addressing space
0 gb
1 gb
2 gb
3 gb
4 gb
P1
P2
Reservedvirtualregion for the system(kernel)
RAM
53
Shared memory mapping (huge)
32 bit addressing space
0 gb
1 gb
2 gb
3 gb
4 gb
P1
P2
RAM
HugePagesPre-AllocatedMemory pool Locked in RAM
54
VLM 32 bit workarround

• 32 bit adress space is 4 Gb
• 32 bit systems with PAE (Intel)
• up to 64 Gb of ram
• Memory filesystem
• opens a file in /dev/shm for buffer cache
• shared pool still in Shared Memory
• Beware of small Oracle block size

55
VLM using 3gb on 32 bit
32 bit addressing space
0 gb
1 gb
2 gb
3 gb
4 gb
P1
P2
/dev/shm/ora_ ramfs
mmap region
RAM
56
USE_INDIRECT_BUFFERS

• RedHat/SUSE
• shmfs needs size
• tmpfs does not need size
• ramfs does not need size Locked
• none can use HugePages
• shared pool can still use HugePages
• double-memory access due to mapping

57
DirectIO

• Direct IO (O_DIRECT) bypasses file system cache
  and access the files directly
• DB activity does not pollute OS cache
• DB activity does not compete with PGA/PLSQL memory

58
PageTables

• Memory for per-process page tables
• B-Tree like structure this number shows leaf
  blocks space
• Memory to manage memory
• One entry of 4 bytes per process, per used 4kb
  of memory
• In Oracles case, assuming an SGA of 2gb524288
  pages 8 bytes 4 Mb per process
• 1000 sessions 4 Gb of memory, to manage 2gb of
  SGA

59
Case studies

• PageTables using a lot of ram

60
PageTables bad example

• Config
• 1.7 Gb sga (max on 32 bit without VLM)
• 1400 Mb in db_cache_size
• table sized to fit exactly in cache
• Start 100 sessions, that full scan the table
  (cached) in order to touch the memory and
  allocate the PTEs
• Sessions will wait via dbms_lock.allocate to be
  released
• Show before and after PageTables usage

61
PageTables bad example cont.

• Before starting the sessions (db is UP)
• cat /proc/meminfo
• MemFree 1070472 kB
• Committed_AS 1881544 kB
• PageTables 4932 kB
• After sessions have finished touching the memory
• cat /proc/meminfo
• MemFree 473496 kB
• Committed_AS 4708552 kB
• PageTables 295068 kB

62
HugePages Oracle

• Locks SGA in memory
• no part of the SGA will ever be swapped out, or
  even considered for swapping
• Reduces the number of PTE entries
• Assuming 2 Gb SGA 1000 PTEs 8 bytes 8 Kb
  per process
• 1000 sessions 4 Mb of memory, a 512 fold
  reduction

63
HugePages Performance

• Releases more memory for PGA or more db_cache
• Guarantees that SGA will always be in memory
• Improves TLB hit ratio
• TLB is a CPU level cache of virtual to physical
  memory mappings, improving performance
• 8 improvement in a memory only TPC test
• not including the fact there is more memory
  available

64
HugePages 100 sessions

• The test from a few slides before
• Before starting 100 sessions (db up)
• cat /proc/meminfo
• Committed_AS 332264 kB
• PageTables 3056 kB
• After
• Committed_AS 3124640 kB
• PageTables 23100 kB

65
No hugepages
System
User
SLAB
Buffers
Mapped
Anonymous (PGA,PLSQL arrays)
Pagetables
Cached
IPC Memory (SGA)
66
With HugePages
System
User
SLAB
Buffers
Mapped
Anonymous (PGA,PLSQL arrays)
Pagetables
Cached
Hugepages
IPC Memory (SGA)
67
HugePages on Red Hat

• what you need to setup RH4
• /proc/sys/vm/nr_hugepages
• /proc/sys/vm/hugetlb_shm_group
• /etc/security/limits.conf

68
Case studies

• Where is my free memory going?

69
Freshly booted

• vmstat 2
• procs -----------memory---------- ---swap--
  -----io---- --system-- ----cpu----
• r b swpd free buff cache si so bi
  bo in cs us sy id wa
• 0 0 0 7725800 13036 497864 0 0
  0 16 1013 25 0 0 100 0
• 0 1 0 7663272 13144 556516 0 0
  14806 70 1164 393 2 2 80 16
• 0 1 0 7513128 13252 706168 0 0
  37494 0 1318 631 2 3 75 20
• 0 1 0 7310824 13408 908032 0 0
  50502 64 1429 862 3 4 75 18
• ...
• 0 1 0 5503208 14724 2709556 0 0
  59144 16 1493 987 3 4 75 18
• 1 0 0 5263080 14856 2948884 0 0
  59838 128 1518 995 3 5 75 18
• 0 0 0 5111272 14944 3106096 0 0
  39344 6 1332 663 2 5 82 11
• 0 0 0 5111272 14944 3106096 0 0
  0 16 1013 26 0 0 100 0
• 0 0 0 5111144 14960 3106080 0 0
  0 30 1016 36 0 0 100 0
• Reading 1.2 Gb of data, free memory drops twice
  as much
• file system cache
• oracle SGA been touched

70
Freshly booted hugepages

• vmstat 2
• procs -----------memory---------- ---swap--
  -----io---- --system-- ----cpu----
• r b swpd free buff cache si so bi
  bo in cs us sy id wa
• 0 0 0 3436280 14236 286324 0 0
  0 56 1027 54 0 0 100 0
• 0 1 0 3395192 14336 323924 0 0
  18902 24 1193 447 2 1 81 16
• 0 1 0 3303928 14480 415040 0 0
  45572 48 1387 775 3 1 75 21
• 0 1 0 2566776 15560 1150020 0 0
  49228 6 1416 828 3 1 75 20
• 0 1 0 2452152 15720 1264260 0 0
  57230 18 1492 977 3 1 75 20
• Reading 1.2 Gb of data, free memory drops with
  same amount
• file system cache consuming memory

71
Freshly booted with directIO

• vmstat 2
• procs -----------memory---------- ---swap--
  -----io---- --system-- ----cpu----
• r b swpd free buff cache si so bi
  bo in cs us sy id wa
• 0 0 0 3436280 14236 286324 0 0
  0 56 1027 54 0 0 100 0
• 0 1 0 3395192 14336 323924 0 0
  18902 24 1193 447 2 1 81 16
• 0 1 0 3303928 14480 415040 0 0
  45572 48 1387 775 3 1 75 21
• 0 1 0 2566776 15560 1150020 0 0
  49228 6 1416 828 3 1 75 20
• 0 1 0 2452152 15720 1264260 0 0
  57230 18 1492 977 3 1 75 20
• 1.2 Gb of data 1.2 Gb drop in free memory
• NO CHANGE

72
DIRECT_IO Bugs

• bug 3186847
• filesystemio_optionsdirectio is ignored on linux
• fixed in 9.2.0.6
• Note 297521.1
• bug 2448994 introduced - O_DIRECT flag was not
  passed to the open() system call
• fixed in 9.2.0.7
• Basically you need 9.2.0.7

73
Shared memory monitoring

• How to see shared memory?
• ipcs shows the IPC shared memory
• If you kill Oracle without freeing up shared
  memory
• ipcrm to remove

74
ipcs

• ipcs
• ------ Shared Memory Segments --------
• key shmid owner perms bytes
  nattch status
• 0x00000000 4915200 oracle 600
  2097152 14
• 0x00000000 4947969 oracle 600
  1342177280 14
• 0x7157be04 4980738 oracle 600
  278921216 14
• ------ Semaphore Arrays --------
• key semid owner perms nsems
  
• 0xb1adfd8c 622592 oracle 640 354
  
• ------ Message Queues --------
• key msqid owner perms
  used-bytes messages

75
To remove orphan segments

• Identified via sysresv
• or number attached from ipcs
• or pmap of an oracle pid
• Use ipcrm to remove

76
The End

• Thank you,
• Questions?
• kutrovsky_at_pythian.com
• Visit my blog at
• http//www.pythian.com/blogs/kutrovsky/

Christo Kutrovsky The Pythian Group 2007 April

• http//www.pythian.com/