Oracle cache and File System cache

on the checkpoint, oracle cache will be written to disk. But, If an oracle database is over file system datafile, it likely that the data are still leave in FileSystem cache. I don't know how could oracle keep data consistency.

Thanks for your feedback. I am almost clear about this issue now, except one point need to be confirmed: do you mean that on linux or unix, if required, we can set "direct to disk" from OS level, but for windows, it's default "direct to disk", we do not need to set it manually.
And I have a further question: If a database is stored on a SAN disk, say, a volume from disk array, the disk array could take snapshot for a disk on block level, we need to implement online backup of database. The steps are: alter tablespace begin backup, alter system suspend, take a snapshot of the volume which store all database files, including datafiles, redo logs, archived redo logs, controll file, service parameter file, network parameter files, password file. Do you think this backup is integrity or not. please note, we do not flush the fs cache before all these steps. Let's assume the SAN cache could be flushed automatically. Can I think it's integrity because the redo writes are synchronous.

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Oracle DB and File system backup configuration

Hi,
As I understand from the help documents and guides, brbackup, brarchive and brrestore are the tools which are used for backing up and restoring the oracle database and the file system. We have TSM (Trivoli Storage manager) in our infrastructure for managing the backup centrally. Before configuring the backup with TSM, I want to test the backup/restore configuration locally i.e. storing the backup to local file system and then restoring from there. Our backup strategy is to have full online backup on the weekends and incremental backup on the weekdays. Given this, following are the things, I want to test.
1. Full online backup (to local file system)
2. Incremental online backup (to local file system)
3. Restore (from local file system)
I found help documents to be very generic and couldn't get any specific information for the comprehensive configuration to achieve this. Can someone help with end to end configuration?
We are using SAP Portal 7.0 (NW2004s) with Oracle 10g database hosted on AIX server.
Helpful answers will be rewarded
Regards,
Chandra

Thanks for your feedback. I am almost clear about this issue now, except one point need to be confirmed: do you mean that on linux or unix, if required, we can set "direct to disk" from OS level, but for windows, it's default "direct to disk", we do not need to set it manually.
And I have a further question: If a database is stored on a SAN disk, say, a volume from disk array, the disk array could take snapshot for a disk on block level, we need to implement online backup of database. The steps are: alter tablespace begin backup, alter system suspend, take a snapshot of the volume which store all database files, including datafiles, redo logs, archived redo logs, controll file, service parameter file, network parameter files, password file. Do you think this backup is integrity or not. please note, we do not flush the fs cache before all these steps. Let's assume the SAN cache could be flushed automatically. Can I think it's integrity because the redo writes are synchronous.

Windows Embedded Standard File system cache

Hey I am new in Windows Embedded.
I am using Windows Embedded Standard XP, and looking for information regarding cache and file system in OS.
File Systems are designed to reduce the disk hits. File write operations does not write to disk immediately until we use the flush API. Flush API makes the system slower though. Os on the other hand keeps flushing the data in optimized way.
We need to know
1- how frequent windows embedded standard is flushing the data. ?
2- How much data it keeps in file system cache(Ram) before flushing ?
3- Can we change things mentioned in above two points by using code?

Ok Thank you very much .
How much data it keeps in file system cache(Ram) before flushing ? How much cache memory i have on ram
How we know this ?

Warming up File System Cache for BDB Performance

Hi,
We are using BDB DPL - JE package for our application.
With our current machine configuration, we have
1) 64 GB RAM
2) 40-50 GB -- Berkley DB Data Size
To warm up File System Cache, we cat the .jdb files to /dev/null (To minimize the disk access)
e.g
// Read all jdb files in the directory
p = Runtime.getRuntime().exec("cat " + dirPath + "*.jdb >/dev/null 2>&1");
Our application checks if new data is available every 15 minutes, If new Data is available then it clears all old reference and loads new data along with Cat *.jdb > /dev/null
I would like to know that if something like this can be done to improve the BDB Read performance, if not is there any better method to Warm Up File System Cache ?
Thanks,

We've done a lot of performance testing with how to best utilize memory to maximize BDB performance.
You'll get the best and most predictable performance by having everything in the DB cache. If the on-disk size of 40-50GB that you mention includes the default 50% utilization, then it should be able to fit. I probably wouldn't use a JVM larger than 56GB and a database cache percentage larger than 80%. But this depends a lot on the size of the keys and values in the database. The larger the keys and values, the closer the DB cache size will be to the on disk size. The preload option that Charles points out can pull everything into the cache to get to peak performance as soon as possible, but depending on your disk subsystem this still might take 30+ minutes.
If everything does not fit in the DB cache, then your best bet is to devote as much memory as possible to the file system cache. You'll still need a large enough database cache to store the internal nodes of the btree databases. For our application and a dataset of this size, this would mean a JVM of about 5GB and a database cache percentage around 50%.
I would also experiment with using CacheMode.EVICT_LN or even CacheMode.EVICT_BIN to reduce the presure on the garbage collector. If you have something in the file system cache, you'll get reasonably fast access to it (maybe 25-50% as fast as if it's in the database cache whereas pulling it from disk is 1-5% as fast), so unless you have very high locality between requests you might not want to put it into the database cache. What we found was that data was pulled in from disk, put into the DB cache, stayed there long enough to be promoted during GC to the old generation, and then it was evicted from the DB cache. This long-lived garbage put a lot of strain on the garbage collector, and led to very high stop-the-world GC times. If your application doesn't have latency requirements, then this might not matter as much to you. By setting the cache mode for a database to CacheMode.EVICT_LN, you effectively tell BDB to not to put the value or (leaf node = LN) into the cache.
Relying on the file system cache is more unpredictable unless you control everything else that happens on the system since it's easy for parts of the BDB database to get evicted. To keep this from happening, I would recommend reading the files more frequently than every 15 minutes. If the files are in the file system cache, then cat'ing them should be fast. (During one test we ran, "cat *.jdb > /dev/null" took 1 minute when the files were on disk, but only 8 seconds when they were in the file system cache.) And if the files are not all in the file system cache, then you want to get them there sooner rather than later. By the way, if you're using Linux, then you can use "echo 1 > /proc/sys/vm/drop_caches" to clear out the file system cache. This might come in handy during testing. Something else to watch out for with ZFS on Solaris is that sequentially reading a large file might not pull it into the file system cache. To prevent the cache from being polluted, it assumes that sequentially reading through a large file doesn't imply that you're going to do a lot of random reads in that file later, so "cat *.jdb > /dev/null" might not pull the files into the ZFS cache.
That sums up our experience with using the file system cache for BDB data, but I don't know how much of it will translate to your application.

888k Error in ULS Logs for File System Cache

Hello,
We have a SharePoint 2010 farm in a three-tier architecture with multiple WFEs and APP servers.
Roughly once a week we will have a number of WFEs seize up and jump to 100% CPU usage. Usually they come in pairs; two servers will jump to 100% at the same time while all the other servers are fine in the 20% - 50% range.
Corresponding to the 100% CPU spike, the following appear in the ULS logs:
"File system cache monitor encoutered error, flushing in memory cache: System.IO.InternalBufferOverflowException: Too many changes at once in directory:C:\ProgramData\Microsoft\SharePoint\Config\<GUID>\."
When these appear, the ULS logs will show hundreds back-to-back flooding the logs.
I have yet to figure out how to stop these and bring the CPU usage down while the incident is happening, and how to prevent them in the future.
While the incident is happening, I have tried clearing the configuration cache, shutting the timer jobs down on each server, deleting all the files but config.ini in the folder listed above, changing config.ini to 1, and restarting the timer. The CPU will
drop momentarily during this process, but as soon as all the timer jobs are restarted the CPUs jump back to 100% on the same servers.
This week as part of my weekly maintenance I thought I'd be proactive and clear the cache even though the behavior wasn't happening, and all CPUs were normal. As soon as I finished, the CPU on two servers that were previously fine jumped to 100% and wouldn't
come down. Needless to say, users complain of latency when servers are at 100% CPU.
So I am frustrated. The only thing I have found that works when the CPUs jump to 100% with these errors are a reboot. Nothing else, including IISReset and stopping/starting the admin and timer job services work. Being Production systems, reboots during the
middle of the day are bad.
Any ideas? I have scoured the Internet resources on this error and have come up relatively empty-handed. All the articles reference clearing the configuration cache, which, in my instance, does not get rid of these issues, and can even trigger them.
Thanks,
Joseph Irvine

Take a look at http://support.microsoft.com/kb/952167 for the list of recommended exclusions per Microsoft.
Trevor Seward
Follow or contact me at...
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This post is my own opinion and does not necessarily reflect the opinion or view of Microsoft, its employees, or other MVPs.

File system cache on APO for ATP

Hi, aces,
Do you have any recommendation percentage of file system cache on AIX for APO/ATP environment? My system was configured to be 20% min -80% max. But I am not sure if this is good for APO/ATP.
I suspect the file system cache takes a lot of memory and leaves less memory for APO work processes.
Regards,
Dwight

sar will give you what you need....

File system cache performance

hi.
i was wondering if anyone could offer any insight into how to
assess the performance of the file system cache. I am interested
in things like hit rate (which % of pages read are coming from the
cache instead of from disk), the amount of data read from the cache
over a time span, etc.
outside of the ::memstat dcmd for mdb, i cannot seem to find a whole lot about this topic.
thanks.

sar will give you what you need....

AIX File system caching

Dear Experts,
How to disable file system caching in aix environment?
Thanks in advance.
Regards,
Rudi

> How to disable file system caching in aix environment?
This depends on the filesystem used.
Check http://stix.id.au/wiki/Tuning_the_AIX_file_caches
Markus

How to create a new user id in OID for Oracle Collab suite File System

Dear Friends,
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Please do the needfull and thanks in advance...
With warm regards
R.Prasad

Hi!
The way you suggest should not be used.
A CS user will be created as a normal OID user and will receive the CS attributes in a different subtree later during the provisioning.
For creating CS users use oesuser and uniuser. Files provisioning will work in a different manner anyway.
cu
Andreas

Query performance problem - events 2505-read cache and 2510-write cache

Hi,
I am experiencing severe performance problems with a query, specifically with events 2505 (Read Cache) and 2510 (Write Cache) which went up to 11000 seconds on some executions. Data Manager (400 s), OLAP data selection (90 s) and OLAP user exit (250 s) are other the other event with noticeable times. All other events are very quick.
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persistent cache across each app server -> cluster table,
update cache in delta process is checked ->group on infoprovider type
use cache despite virtual characteristics/key figs checked (one info-cube has1 virtual key figure which should have a static result for a day)
=>Do you know how I can get more details than what's in 0TCT_C02 to break down the read and write cache events time or do you have any recommandation?
I have checked and no dataloads were in progres on the info-providers and no master data loads (change run). Overall system performance was acceptable for other queries.
Thanks

Hi,
Looks like you're using BDB, not BDB JE, and this is the BDB JE forum. Could you please repost here?:
Berkeley DB
Thanks,
mark

Difference between Presentation Server Cache and BI Server Cache

Hello Experts,
What is the Diff b/w Presentation Server Cache and BI Server Cache
Thanks,
S Gouda

Hello,
Okay, what do you want to do about caching at BI server and Presentation server.
A nQSXXXX.tmp is a temporary cache file which maintained by the BI Server for an analysis request by a user and is kind of shared data between the OBI Server and the OBI Presentation server. This is refereed as the 'Cursor Cache' which could be managed by going thru Administration> Manage Sessions > Clear Cursor Cache.These .tmp files are it is not related to BI Server cache.
By Default, the BI Server Cache is stored in the and stored as NQSxxxxx.tbl files. [middlware_home]/instances/instance1/bifoundation/OracleBIServerComponent/coreapplication_obis1/cache]
Caching occurs by default at the subrequest level, which results in multiple cache entries for some SQL statements. Caching subrequests improves performance and the cache hit ratio, especially for queries that combine real-time and historical data.
Below are some useful links for cache management in OBIEE 11g.
http://oraclebisolutions.blogspot.com/2013/02/obiee-11g-obi-server-and-presentation.html
http://drazda.blogspot.com/2012/10/obiee-11g-cache-management.html
http://allaboutobiee.blogspot.in/2012/03/cache-management-purging-cache.html
Pls mark itf this helps. Else post the exact questions you have about this post.
Thanks,
SVS

How to bulk import data into CQ5 from MySQL and file system

Is there an easy way to bulk import data into CQ5 from MySQL and file system? Some of the files are ~50MB each (instrument files). There are a total of ~1,500 records spread over about 5 tables.
Thanks

What problem are you having writing it to a file?
You can't use FORALL to write the data out to a file, you can only loop through the entries in the collection 1 by 1 and write them out to the file like that.
FORALL can only be used for SQL statements.

Oracle JVM and Operating System JVM different?

Are Oracle JVM and Operating System JVM different?
For applying the DST patches if JVM is updated from OS patches do we need to apply any other jvm patches again?

Hi,
Yes, the OracleJVM is embedded in the RDBMS kernel and does not share any reference/components with the JDK (i.e., OS JVM); fwiw, you can learn more about OracleJVM (archtecture, memory management, security, threading, performance) in chapter two of my book.
Regarding the DST patch, there is an RDBMS patch that should cover OracleJVM as well; Re: How to verify if the DST patch applied correctly or not.
Kuassi http://db360.blogspot.com

LOCAL OLAP CACHE AND GLOBAL OLAP CACHE

what is local olap cache and global olap cache...
what is the difference between ....can you explain scenario plz...
will reward with points
thanks in advance

Hello GURU
Local cache is specific to a user, before BW 3.0 it was only local cache available...if a user run the query data will come to cache from infoprovider and next time same query will not go to Data base instead it will fetch data from cache memory...this cache will be used only for that particular user...if some other user try the same query it will not pick up dta from cache.....
BW 3.0 onward we have global cache which means several user can access same cache for the same query or data which is related in cache...
Thanks
Tripple k

Oracle 11g /proc file system files on Linux x86-64

OS: RHEL 5.6
Oracle: 11.2.0.3 Standard Edition RAC (GI and DB)
In 11.2.0.3, it is found that the pseudo files for Oracle processes in /proc filesystem were owned by root, even though the process owner is oracle.
[oracle@dbserver proc]$ ps -ef|grep ckpt
oracle    7358     1 0 Dec17 ?        00:00:46 ora_ckpt_orcl1
oracle   28190 27544 0 12:08 pts/1    00:00:00 grep ckpt
[oracle@dbserver proc]$ cd /proc/7358
[oracle@dbserver 7358]$ ls -l
ls: cannot read symbolic link cwd: Permission denied
ls: cannot read symbolic link root: Permission denied
ls: cannot read symbolic link exe: Permission denied
total 0
dr-xr-xr-x 2 oracle asmdba 0 Dec 19 12:08 attr
-r-------- 1 root   root   0 Dec 19 12:08 auxv
-r--r--r-- 1 root   root   0 Dec 19 10:58 cmdline
-rw-r--r-- 1 root   root   0 Dec 19 12:08 coredump_filter
-r--r--r-- 1 root   root   0 Dec 19 12:08 cpuset
lrwxrwxrwx 1 root   root   0 Dec 19 12:08 cwd
-r-------- 1 root   root   0 Dec 19 12:08 environ
lrwxrwxrwx 1 root   root   0 Dec 19 12:08 exe
dr-x------ 2 root   root   0 Dec 17 22:17 fd
dr-x------ 2 root   root   0 Dec 19 12:08 fdinfo
-r--r--r-- 1 root   root   0 Dec 19 12:08 io
-r--r--r-- 1 root   root   0 Dec 19 10:58 limits
-rw-r--r-- 1 root   root   0 Dec 19 12:08 loginuid
-r--r--r-- 1 root   root   0 Dec 19 12:08 maps
-rw------- 1 root   root   0 Dec 19 12:08 mem
-r--r--r-- 1 root   root   0 Dec 19 12:08 mounts
-r-------- 1 root   root   0 Dec 19 12:08 mountstats
-r--r--r-- 1 root   root   0 Dec 19 12:08 numa_maps
-rw-r--r-- 1 root   root   0 Dec 19 12:08 oom_adj
-r--r--r-- 1 root   root   0 Dec 19 12:08 oom_score
lrwxrwxrwx 1 root   root   0 Dec 19 12:08 root
-r--r--r-- 1 root   root   0 Dec 19 12:08 schedstat
-r--r--r-- 1 root   root   0 Dec 19 12:08 smaps
-r--r--r-- 1 root   root   0 Dec 19 10:59 stat
-r--r--r-- 1 root   root   0 Dec 19 10:58 statm
-r--r--r-- 1 root   root   0 Dec 19 10:58 status
dr-xr-xr-x 3 oracle asmdba 0 Dec 19 12:08 task
-r--r--r-- 1 root   root   0 Dec 19 11:00 wchanAs a result, many diagnostic utility, like the /proc filesystem (especially the fd/ subdirectory), lsof, strace, gdb, ... were not usable by the the oracle OS account. Any idea?
In 10g + RHEL 5.2, the psuedo files were owned by oracle.

sb92075 wrote:
different system, different OS, & different permissions which has NOTHING to do with Oracle RDBMSDon't agree. Permissions, ownership, etc could be reconfigured while process spawn, this is surely related to Oracle Software. (Well, you may argue that it is related to GI only. But the situation is the same for standalone DB running on standalone ASM).

Oracle cache and File System cache

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