Question about Lock Duration

Hi,
I found a description at this link.
http://help.sap.com/saphelp_nw04/helpdata/en/41/7af4c5a79e11d1950f0000e82de14a/content.htm
'At the end of an SAP LUW, you should release all locks. This either happens automatically during the database update, or explicitly, when you call the corresponding dequeue function module. Locks that are not linked to a database update are released at the end of the SAP transaction'
I don't understand this, because I tested using commit work and wait. The lock entry still there after the statement 'commit' executed. the lock entry disappeared when the whole task completed.
don't know what does happens automatically during the database update. Isn't the 'commit' the case they mentioned?

So does that means even I using a SYNCHRONIZE commit. There still not a database update happen?
From help.sap.com:
For 'commit work' "It triggers a database commit that also terminates the current database LUW and closes all database cursors. "
Database commit <> database update ?

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A string of question about Locking & Isolation Level

Hi All
It is highly appreciated if someone give offer answers to my below questions
1) There are two ways of locking mechanism: Pessimistic & Optimistic. In general, do all J2EE app server support all these two ways of locking ?
2) It seems to me that setting the isolation level to "serialization" should result in using pessmistic locking. If no so, please point out my misconcept and explain to me.
3) Are there any differences in the way of entity bean programming as different locking mechansim is adopted ?
4) With regard to optimistic locking, will the app server throw out exception as data contention is detected ? Is the way of handling dependent on app server? Or It is transparent to the developer of entity bean. Please give me an e.g of j2ee app server product how to handle this scenario.
5) To adopt the approach of "optimistic" locking, do l have to implement it on my own using bean managed entity bean.
6) It seems to me that optimistic locking can achieve better concurrency. If it is inherently supported by app server for its container managed entity bean (=> totally transparent to the developer of entity bean). Is it always the rule of thumb to config the server to use "optimistic" locking instead of "pessimistic" ?
Sorry for bombarding you guys with such long list of questions. l would be very thankful if someone can help me consolidate my concept on these topics.
Also, please send your reply to [email protected] as well
thanks & regards
Danny

Hi Danny,
I became interested about the optimistic locking recently. If the topic is not long forgotten then this may make some difference!
We have attacked the optimistic locking issue by introducing audit fields (MODIFY_BY_USER, MODIFY_DATE) in tables where concurrency needs to be implemented.
We are retrieving rows from the table (for display or update) through Stateless Session Bean using simple SQL SELECT. The audit fields are fetched along with the business data and are kept at the client. While any of the concurrent users tries to update the row the audit fields are sent to the application server along with the modified business data. The relevant Entity Bean checks for any difference in the timestamp of the audit field (MODIFY_DATE) value with the value in the database. If a mismatch is found it reports a business exception to the user. Otherwise, the row is updated with the lastest timestamp value in the audit field MODIFY_DATE.
This works fine when two update operations are not concurrent, i.e., two users submit their update requests in a time lag greater than the time taken by the transaction to complete. This alone could not prevent the dirty update on the database.
Hence, to prevent any concurrent update contending for the same row you need to set the following ejbgen tag in the Entity Bean:
concurrency-strategy = Exclusive<<<<<Note: We are using Weblogic 6.1 with SP4 and CMP (no BMP).
Please let me know if you have got a better solution to tackle this issue.
Chandra.

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Dear all.
I have a merge query with a decedent hint to prevent deadlock with another queries.
Another queries use select ~for update with same hint.
My question is that the locking order will follow the hint in this query?
Or I might use the select ~ for update before this merege.
Please give any advice about select ~for update and locking order in the query.
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Two basic questions about locks in Oracle.

Hello,
This is about 9i and onwards.
I need to develop a comprehensive analysis of locks and waits and while doing so, following questions popped up.
1) What is the difference between locks and waits?
2) There is a DBA view called DBA_BLOCKERS. The standard Oracle documentation has only one line comment about this view i.e. "DBA_BLOCKER – Shows non-waiting sessions holding locks being waited-on by other sessions.
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Thanks,
R

1) What is the difference between locks and waits? Lock - something you queue up to get and simply wait until it is available
Waits - Waiting for a Specific event to happen before it can proceed.
Re: Difference between a latch and a lock
2) There is a DBA view called DBA_BLOCKERS. The standard Oracle documentation has only one line comment about this view i.e. "DBA_BLOCKER – Shows non->waiting sessions holding locks being waited-on by other sessions.DBA_BLOCKERS displays a session if it is not waiting for a locked object but is holding a lock on an object for which another session is waiting.
HTH
-Anantha

Question about locking certain folders w/diff.accounts?

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Hi Aaron
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Hi, I'm making a small video clip with photos. The photo's are6 seconds long and I want to cut them down to about 4 seconds. Right now I'm selecting them one by one and changing the duration of them to 4 seconds. Is there any easier way for me to do this?
I'm also putting a video transition between every photo in the clip, is there any way that I can select all of them and add the transition to all of them at the same time?
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Question about lock

Hi all,
I would like to know what table/object is locked during a goods movement?
And also, can I lock a batch? If yes, what FM can I used to check whether a batch is being locked or not?
Thanks in advance.

Hi,
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CS

Question about locking down IIS on an SCCM 2012 distribution point on a Windows Server 2003

Hello. My environment is SCCM 2012 SP1. I will be setting up several distribution points on Windows Server 2003 machines. This summer I have a project to configure SCCM to use our PKI infrastructure. Unfortunately, this will not be in place before I need
to set the Windows Server 2003 machines up as distribution points. I am not an IIS expert. When I set the DPs up, I am only 1)Installing IIS, 2)Enabling BITS extensions, and 3)Enabling WebDav. Is there anything I should do to ensure they are as secured as
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Edited by: Rob Burbank on Dec 3, 2009 4:29 PM

FSKB G/L Account Posting
this transaction is not working

Questions on Locking-- URGENT

Here are my questions on Locking.:
1)
How do I use v$lock to figure out lock details ? Details like
whos has locked,on which table,who else is waiting, and what type
of locking (shared or exlusive ?), since when it is locked.
2)
Why and when exclusive/shared locks are used ? Could you give me
example please ?
3)
Could you tell me significance of v$mystat and v$locked_object ?
4)
Do we have page level locking in Oracle ?
Thanks in advance,
DN

Details about locks : All locks acquired by statements within a transaction are held for the duration of the transaction.
Oracle releases all locks acquired by the statements within a transaction when an explict or implied commit or roll back is executed. Oracle also releases locks acquired after a savepoint when rolling back to the savepoint.
Note: Only transactions not waiting for the previously locked resources can acquire locks on now available resources. Waiting transactions continue to wait until after the original transaction commits or completely rolls back.
1. How do I use v$lock to figure out lock details? Details like
whos has locked,on which table,who else is waiting, and what type
of locking (shared or exlusive ?), since when it is locked.
Better way is to use Oracle OEM. The TYPE column in v$lock shows the type of wait events and we also have the LMODE column (lock mode) and REQUEST columns.
Here is a comprehensive v$lock query by Deepak Baranwal, listing the lock types:
set echo off
col sid form 9999
col id1 form 9999999999
col id2 form 999999999
col lmode head "Lock Held" form a14
col request1 head "Lock Request" form a16
col type head "Lock Type" form a15
col ctime head "Time|Held" form 999999
col block head "No Of |Sessions|Waiting|For This|Lock" form 99999
select sid,
DECODE(TYPE,
'BL','Buffer hash table',
'CF','Control File Transaction',
'CI','Cross Instance Call',
'CS','Control File Schema',
'CU','Bind Enqueue',
'DF','Data File',
'DL','Direct-loader index-creation',
'DM','Mount/startup db primary/secondary instance',
'DR','Distributed Recovery Process',
'DX','Distributed Transaction Entry',
'FI','SGA Open-File Information',
'FS','File Set',
'IN','Instance Number',
'IR','Instance Recovery Serialization',
'IS','Instance State',
'IV','Library Cache InValidation',
'JQ','Job Queue',
'KK','Redo Log "Kick"',
'LS','Log Start/Log Switch',
'MB','Master Buffer hash table',
'MM','Mount Definition',
'MR','Media Recovery',
'PF','Password File',
'PI','Parallel Slaves',
'PR','Process Startup',
'PS','Parallel Slaves Synchronization',
'RE','USE_ROW_ENQUEUE Enforcement',
'RT','Redo Thread',
'RW','Row Wait',
'SC','System Commit Number',
'SH','System Commit Number HWM',
'SM','SMON',
'SQ','Sequence Number',
'SR','Synchronized Replication',
'SS','Sort Segment',
'ST','Space Transaction',
'SV','Sequence Number Value',
'TA','Transaction Recovery',
'TD','DDL enqueue',
'TE','Extend-segment enqueue',
'TM','DML enqueue',
'TS','Temporary Segment',
'TT','Temporary Table',
'TX','Transaction',
'UL','User-defined Lock',
'UN','User Name',
'US','Undo Segment Serialization',
'WL','Being-written redo log instance',
'WS','Write-atomic-log-switch global enqueue',
'XA','Instance Attribute',
'XI','Instance Registration',
decode(substr(TYPE,1,1),
'L','Library Cache ('||substr(TYPE,2,1)||')',
'N','Library Cache Pin ('||substr(TYPE,2,1)||')',
'Q','Row Cache ('||substr(TYPE,2,1)||')',
'????')) TYPE,
id1,id2,
decode(lmode,
0,'None(0)',
1,'Null(1)',
2,'Row Share(2)',
3,'Row Exclu(3)',
4,'Share(4)',
5,'Share Row Ex(5)',
6,'Exclusive(6)') lmode,
decode(request,
0,'None(0)',
1,'Null(1)',
2,'Row Share(2)',
3,'Row Exclu(3)',
4,'Share(4)',
5,'Share Row Ex(5)',
6,'Exclusive(6)') request1,
ctime, block
from
v$lock
where sid>5
and type not in ('MR','RT')
order by decode(request,0,0,2),block,5
2 .Why and when exclusive/shared locks are used ? Could you give me
example please ?
Exclusive Lock Mode : Prevents the associates resource from being shared. This lock mode is obtained to modify data. The first transaction to lock a resource exclusively is the only transaction that can alter the resource until the exclusive lock is released.
Share Lock Mode : Allows the associated resource to be shared, depending on the operations involved. Multiple users reading data can share the data, holding share locks to prevent concurrent access by a writer (who needs an exclusive lock). Several transactions can acquire share locks on the same resource.
Oracle Lock Types
DML locks (data locks)
DDL locks (dictionary locks)
Oracle Internal Locks/Latches
Oracle Distributed Locks
Oracle Parallell Cache Management Locks
3. Could you tell me significance of v$mystat and v$locked_object ?
v$locked_object show the information about Who is locking and what object they locking. This view is similar to v$mystat except that it shows cumulated statistics for all sessions.
4. Do we have page level locking in Oracle ? No
Sachin

Questions about your new HP Products? HP Expert Day: January 14th, 2015

Thank you for coming to Expert Day! The event has now concluded.
To find out about future events, please visit this page.
On behalf of the Experts, I would like to thank you for coming to the Forum to connect with us. We hope you will return to the boards to share your experiences, both good and bad.
We will be holding more of these Expert Days on different topics in the months to come. We hope to see you then!
If you still have questions to ask, feel free to post them on the Forum – we always have experts online to help you out.
So, what is HP Expert Day?
Expert Day is an online event when HP employees join our Support Forums to answer questions about your HP products. And it’s FREE.
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It’s easy. Come out to the HP Support Forums, post your question, and wait for a response! We’ll have experts online covering our Notebook boards, Desktop boards, Tablet boards, and Printer and all-in-one boards.
We’ll also be covering the commercial products on the HP Enterprise Business Community. We’ll have experts online covering select boards on the Printing and Digital Imaging and Desktops and Workstations categories.
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Looking forward to seeing you on January 14th!
I am an HP employee.

My HP, purchased in June 2012, died on Saturday. I was working in recently installed Photoshop, walked away from my computer to answer the phone and when I came back the screen was blank. When I turned it on, I got a Windows Error Recovery message. The computer was locked and wouldn't let me move the arrow keys up or down and hitting f8 didn't do anything.
I'm not happy with HP. Any suggestions?

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Question about Lock Duration

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