Problem with Real memory and swap file

[solvetek]

RS/6000 S85
AIX 4.3.3.0
8GIG Ram
3GIG SWAP File
Oracle 8.1.6

Each day our swap file percent used goes up and at the same time, we have huge amounts of real memory free. Is it normal for AIX to increase swap file from 121MB to 1694MB when there is 4805MB of free real memory? I thought UNIX only used swap file when real memory was exhausted. If this is a problem does anyone know what might be causing it or how to debug it?

Day 1
Memory Real Virtual Paging (4kB)
free 4591 MB 2950 MB 363.4 pgfaults
procs 2255 MB 121 MB 363.3 pgin
files 1345 MB 44.4 pgout
total 8192 MB 3072 MB 0.4 pgsin
21.4 pgsout

Day 2
Memory Real Virtual Paging (4kB)
free 4805 MB 1377 MB 436.3 pgfaults
procs 1748 MB 1694 MB 3.6 pgin
files 1637 MB 53.9 pgout
total 8192 MB 3072 MB 0.6 pgsin
2.7 pgsout

 

[MikeLacey]

the swap file, or paging space, is used up whenever a process starts -- unix needs to be sure that it has enough swap/paging space as it start each process, so it allocates paging space in case it needs to page out the whole process if memory gets short

as to why it keeps on consuming more paging space....

not sure, that's a lot of memory there - what does your server do? Mike
michael.j.lacey@ntlworld.com
Email welcome if you're in a hurry or something -- but post in tek-tips as well please, and I will post my reply here as well.

 

[solvetek]

This is an oracle database server running oracle financials.
We have a boat load of datafile for this database about 2000 in total. The physical database size is 43 gig.

below is a copy of our vmstat during normal usage. I do not understand why there is so much paging when we have so much free memory.

---- ----------- ------------------------ ------------ -----------
r b avm fre re pi po fr sr cy in sy cs us sy id wa
1 2 697988 1124996 0 2 0 0 0 0 934 3826 382 1 21 76 1
1 2 697721 1125277 0 0 0 0 0 0 912 1339 456 2 19 79 0
1 2 697722 1125265 0 7 0 0 0 0 894 906 356 1 19 79 1
2 2 697454 1125542 0 3 0 0 0 0 938 13928 6236 2 22 75 1
2 2 697455 1125540 0 0 0 0 0 0 951 1062 456 0 19 80 1
2 2 697179 1125827 0 0 0 0 0 0 854 765 279 0 20 80 0
3 3 697218 1125783 0 5 0 0 0 0 914 1993 580 4 20 76 1
2 2 697900 1125077 0 1 0 0 0 0 894 3178 317 1 21 77 0
1 2 697221 1125769 0 10 0 0 0 0 926 1819 342 1 20 77 1
1 2 697249 1125832 0 13 0 129 5085 0 953 12262 6645 4 22 72 2
1 3 697340 1125719 0 23 0 0 0 0 970 4890 492 4 22 71 3
4 2 697849 1124800 0 13 0 0 0 0 1008 17756 528 4 22 67 7
1 4 698386 1124310 0 12 256 385 3034 0 1291 2816 896 2 18 59 21
2 4 698478 1124116 0 40 70 258 5347 0 1173 13196 4728 8 20 57 14
1 4 698959 1123509 0 72 77 129 839 0 1120 8018 2837 12 18 57 12
2 3 699249 1123262 0 93 106 258 2132 0 1170 3795 642 14 18 55 13
1 4 699835 1122840 0 12 191 386 2267 0 1258 2929 711 12 16 54 18
4 2 700156 1122626 0 20 121 128 649 0 1172 2167 626 10 16 60 14
2 3 700609 1122186 0 50 33 129 430 0 1103 5276 638 18 18 54 10
3 2 701227 1121352 0 187 0 0 0 0 1214 14765 7040 15 20 55 11
kthr memory page faults cpu
----- ----------- ------------------------ ------------ -----------
r b avm fre re pi po fr sr cy in sy cs us sy id wa
2 8 701383 1121084 0 124 0 129 1330 0 1106 4210 974 11 17 52 20
2 4 701448 1120839 0 135 0 129 1013 0 1176 4121 1274 9 22 50 19
2 3 702433 1119722 0 142 0 259 4214 0 1179 1498 1641 12 21 51 16
2 3 704338 1117697 0 146 0 263 1564 0 1163 2653 1301 14 22 45 19
1 2 704376 1117567 0 36 0 0 0 0 1101 14524 6339 9 24 62 6
2 4 704409 1117482 0 41 0 0 0 0 1016 5885 1027 12 22 62 4
2 5 704447 1117215 0 210 0 128 649 0 1495 1907 3421 10 22 37 31
2 5 704826 1116445 0 227 0 258 2248 0 1429 7868 2578 12 23 36 29
q
2 5 704925 1116178 0 198 0 258 2497 0 1319 14496 1537 15 22 34 30
2 5 704948 1115899 0 179 0 129 726 0 1242 13958 7216 15 22 41 22

 

[bjverzal]

/usr/samples/kernel/vmtune -p 5 -P 10. These are recommended setting for Oracle. They will keep the executables on disk and keep the Oracle database files in memory.

Also - run /usr/samples/kernel/vmtune and look at minfree and maxfree numbers.

I would also look into increasing the size of you SGA. That would buffer more of your writes and reads.

Bill.