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	File locking - Wikipedia, the free encyclopedia
		Most operating systems support the concept of record locking which means that individual records within any given file may be locked, so increasing the number of concurrent update processes.
		Note that the region of the file being locked is not required to have data within the file and applications sometimes exploit this ability to implement their functionality.
		Byte range locking type is determined by the dwFlags parameter in the LockFileEx function used to lock a region of a file.
	en.wikipedia.org /wiki/File_locking (1575 words)

	Manual - Locking and Concurrency
		The pessimistic record locking model specifies that a record should be locked when the record is retrieved for editing, which is during a call to the TDBISAMTable or TDBISAMQuery Edit method or during the record retrieval in an UPDATE SQL statement.
		The two record locking protocols can safely and reliably be used among multiple sessions on the same set of tables, although it is not recommended due to the potential for confusion for the developer and user of the application.
		Record locks are used to enforce DBISAM's pessimistic or optimistic record locking protocols and prevent the same or multiple sessions from editing or posting modifications to the same record at the same time.
	www.elevatesoft.com /dbisam4d7_locking_concurrency.htm (1995 words)

	Articles: Record locking in Web applications
		This lock can persist while the user completes their particular transaction, at which time the user would either save an edited version of the record or log out of the application, thus ending the session.
		Until the record is saved, anyone attempting to retrieve the record would be informed that the record is locked and would only be able to retrieve the information as ‘read only’.
		This approach could be amended for those applications where editing a record may take place in more than one page so that when a user navigates to the next page in the edit sequence, the lock timestamp is updated to ensure that the lock is not released while a user is still editing a record.
	www.ukpua.org /archives/articles/recordlocking.html (1673 words)

	Firebird for the Database Expert: Episode 5 - Locking and Record Versions
		The strategy of incrementally locking records and releasing all locks simultaneously at the end of the transaction is called two-phase locking.
		Those abstract locks are called predicate or existence locks, locks that keep something new from being added to a result set, either by inserting a new record or modifying an existing record so it meets the criteria for the result set.
		Because records are tagged with their version and every transaction knows what transactions are currently active, no transaction can read a record version created by an active transaction.
	www.ibphoenix.com /main.nfs?a=ibphoenix&page=ibp_expert5 (1381 words)

	Record Locking (Site not responding. Last check: 2007-11-01)
		Record locking is a capability which is required for many applications, notably, for database applications.
		Using advisory record locking, if an application accesses a locked record, the operation is permitted with no indication from the implementation that a lock was violated.
		This implies that even if the client implementation supports record locking, that client may be accessing a server which cannot support record locking and/or may be accessing a server using a protocol which does not support record locking.
	www.itl.nist.gov /div897/staff/barkley/titleissues/node13.html (308 words)

	Record Locking - Dev Shed
		When a record is being used by a user all other users are asked to wait untill they are finished.
		This function can be used to implement application locks or to simulate record locks.
		However, working with table locks is not that tough, and unless your application has to do some serious selects, like a ton of data, you should be OK with speed.
	forums.devshed.com /mysql-help-4/record-locking-13406.html (503 words)

	Command Record Locking
		A record is locked when one of the other users or processes has successfully loaded the record for modification.
		If the record is locked by another user, the record is loaded as a locked record that cannot be modified by the local user.
		A record may also be loaded for a related table by any of the commands that cause an automatic relation to be established.
	www.4d.com /docs/CMU/CMU10080.HTM (1645 words)

	Record locking - Achievo/ATK Wiki
		Now that record locking has been implemented the user interface is changed to reflect that it is being used.
		This is a visual indication to the user that record locking is being used.
		To find out which user has a record locked use the tool tip that is presented when the mouse is hovered over top of the gold lock.
	www.achievo.org /wiki/Record_locking (856 words)

	The Old Joel on Software Forum - Access Database - Table/Record Locking with ADO
		Record locking only occurs when you use the DAO “edit”, or ADO modifies the record.
		Locking approaches that use an "islocked" field in the real database fail the "user went to lunch" test, and require giving users a way to request a lock override -- messy.
		When one user begins a transaction and adds a record to the table, any other user trying to add a record is locked out until the first user ends the transaction or rollsback.
	discuss.fogcreek.com /joelonsoftware/default.asp?cmd=show&ixPost=47300 (2650 words)

	Chapter 17. File and Record Locking
		The MS Windows network administrator needs to be aware that file and record locking semantics (behavior) can be controlled either in Samba or by way of registry settings on the MS Windows client.
		Record locking semantics under UNIX are very different from record locking under Windows.
		Opportunistic locking (oplocks) is invoked by the Windows file system (as opposed to an API) via registry entries (on the server and the client) for the purpose of enhancing network performance when accessing a file residing on a server.
	us1.samba.org /samba/docs/man/Samba-HOWTO-Collection/locking.html (4712 words)

	Chapter 14. File and Record Locking
		The limitation of opportunistic locking is the reliability of the mechanism to process an oplock break (notification) between the server and the caching client.
		Opportunistic locking is by default set to "on" by Samba on all configured shares, so careful attention should be given to each case to determine if the potential benefit is worth the potential for delays.
		Opportunistic locking essentially means that the client is allowed to download and cache a file on their hard drive while making changes; if a second client wants to access the file, the first client receives a break and must synchronise the file back to the server.
	www.it.lut.fi /~doc/samba-3.0.0beta3/htmldocs/locking.html (4791 words)

	Locking and Multi-User Access
		Locking prevents users from reading data being changed by other users, and prevents multiple users from changing the same data at the same time.
		Record lock blocks other attempts of locking this record, but do not block read of the locked record.
		Locks are held for the length of time needed to protect the resource at the level requested.
	www.componentace.com /help/absdb_manual/lockingandmulti_useraccess.htm (969 words)

	OpenVMS ask the wizard - RMS Record Locking, File Contention? (Site not responding. Last check: 2007-11-01)
		"RECORD LOCKED BY ANOTHER USER", even though the first program completed operations with this record (the other records are free for access).
		In this particular case, you will need to disable all record locks and maintain your own file-level and record-level access coordination, or manually release the record lock via explicit program request, or implicitly release the record lock by selecting another record in the file.
		A typical pattern involves either waiting for the record lock (via RAB$L_ROP WAT option, and potentially adding the TMO option), or by periodically retrying access to the record.
	h71000.www7.hp.com /wizard/wiz_6326.html (440 words)

	Database Journal Forums - record locking (Site not responding. Last check: 2007-11-01)
		I have a database programmer who in his latest application has deployed manual record locking into code to release certain records to certain users of the application at specified times.
		Essentially you are telling the lock manager that you will handle the locking manually, therefore the lock manager does not need to maintain the extra memory.
		Many people make the mistake of thinking that locks are a bad thing and because they don't understand how locking works or isolation levels work, they get into all sort of trouble.
	forums.databasejournal.com /showthread.php?t=9237 (1102 words)

	Locking Recordsets in Microsoft Access 2000
		In this scenario, although the lock occurs for a very short period of time, it's actually being issued when the data is first edited; then released at the update.
		The disadvantage is that the time between the edit and the update might force the lock to persist for a significant period of time, locking other users out of not only that record, but if page locking is used, the entire page of records the edited record is in.
		In the case of batch optimistic locking, the records are not locked until the UpdateBatch method is issued.
	www.developer.com /tech/article.php/721911 (1019 words)

	► » Record locking (Site not responding. Last check: 2007-11-01)
		I have a puzzling situation that I assume is due to an error in record
		record, but once added it can't be modified or deleted.
		received is that someone else has modified the record at the same time and
	www.accessspots.org /Record-locking-3604869.html (1494 words)

	4.14 Using File and Record Locking
		For example, if a program has a record locked, it is assumed that at some point the program will unlock the record.
		The first program locks file A. The second program locks file B. Then, the first program tries to lock file B. Since the file is locked, the first program waits for the file to be unlocked.
		If no deadlock detection is done and the second program decides to wait for the lock, the two programs become deadlocked: the first is waiting to lock file B and the second is waiting to lock file A. Neither program will ever continue because both are waiting.
	www.conetic.com /helpdoc/cbautil/cbautil00000247.html (822 words)

	Chapter 15. File and Record Locking (Site not responding. Last check: 2007-11-01)
		The first is record locking that allows a client to lock a range of bytes in a open file.
		You can also disable byte range locking completely by using locking = no. This is useful for those shares that do not support locking or do not need it (such as CDROMs).
		It is not really file locking, but is included in most discussions of Windows file locking, so is considered a de facto locking feature.
	info.ccone.at /INFO/Samba/Samba-HOWTO-Collection/locking.html (4818 words)

	DEMYSTIFY FORMS DATA ENVIRONMENTS, DATA SESSIONS AND RECORD LOCKING STRATEGIES (Site not responding. Last check: 2007-11-01)
		This caused a record to be placed in memory where every field had a memory variable that was equal to the name of the field.
		In the case of locking a record this is mostly done for the purpose of modifying it.
		If such is the case all controls are enabled that need to be enabled, in the case of a record update the table is updated, the record is then unlocked, the controls are disabled again and all buttons (either on a toolbar or on a form) are reset to dis/enabled.
	www.foxite.com /articles/052.htm (1946 words)

	Xtreme Visual Basic Talk - Help with multiuser Record Locking Problem
		They need to be able to each grab a single record, edit, update and grab another new record.
		The record grabbed by an individual user needs to be unique.
		If it is a locking error, do an err.clear and use a goto (did I just say that) to a label just above your sql execute statement and let it try again.
	www.xtremevbtalk.com /showthread.php?t=3746 (292 words)

	ACC2000: Record-Level Locking Does Not Appear to Work
		In other words, all records that fit within the 4 kilobyte (4096 byte) page will be locked, even though only one of the records within that page is being edited.
		With record-level locking, however, if a user edits any one record in a table, other users are able to edit any other record, except that one.
		Note that although record-level locking is invoked, you are allowed to edit the value in both instances.
	support.microsoft.com /default.aspx?scid=kb;en-us;225926 (566 words)

	Record Locking. - dBforums
		in a transaction for the locks to be held.
		my feeling is that most do indeed use their own locking scheme in these cases.
		modify the record, you can determine whether the current row is locked.
	www.dbforums.com /showthread.php?t=727038 (1461 words)

	JavaRanch Big Moose Saloon: Record level locking (Site not responding. Last check: 2007-11-01)
		Locking is highly database dependent, and should generally not be manually done by the application.
		page locking: where storage is allocated to pages of data, and the page is locked.
		Depending upon what you are doing you might end up do a table lock because of the number of records selected in the where clause.
	saloon.javaranch.com /cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic&f=3&t=000971 (450 words)

	Achieve Record locking with Access 2000
		Well there is a way to lock records on MSAccess 2000 tables.
		lock the record, or check if it is locked.
		the program, empty the lock table by using a query like 'delete from lock'.
	www.howtodothings.com /computers/a1253-achieve-record-locking-with-access-2000.html (374 words)

	Locking a record against deletion. (Site not responding. Last check: 2007-11-01)
		You can store the username of the "owner" of the record in the table and then write a BEFORE DELETE trigger which checks the username and raises an exception if CURRENT_USER is anyone other than the owner of the record.
		This will allow only the owner of the record to delete the record.
		If you change the owner field to some value that is not the username of any database user, then nobody accessing the database will be able to delete the record, including the person who inserted the record.
	bdn.borland.com /article/0,1410,30149,00.html (137 words)

	[Tutor] Re: Record Locking and Access - newbye (Site not responding. Last check: 2007-11-01)
		But when a user edits an existing record I puzzled to think >that another user might be changing that record at the same time (because >they are not locking any records and are using lists with the record >contents locally)!
		This could cause for example that user A changes record >1 >from "bar" to "foo" and updates the db, just after user A user B updates >the >db with a change in the same record from "bar" to "foobar" (never seeing >user As changes)!!!
		Actually, either way, your app will probably need to know something about the fact that records might need to be locked so that it can let the user know what is happening.
	mail.python.org /pipermail/tutor/2004-June/030118.html (383 words)

	Dr. Dobb's \| AJAX & Record Locking \| September 8, 2006
		Now Client B is unwittingly modifying a record that is no longer current, and when Client B saves the record, the changes made by Client A are lost.
		If the server could push information about locked records to clients, this situation would be remedied, but there really is no good web-oriented push technology.
		That trip to the server places an entry in a map denoting what record is locked, and by which editor.
	www.ddj.com /dept/lightlang/192700218 (937 words)

	ChannelWeb Encyclopedia
		The structure of a file is known to the software that manipulates it.
		For example, database files are made up of a series of records.
		Formatting and other types of information are contained in headers or interspersed throughout the file.
	www.channelweb.com /encyclopedia/defineterm.jhtml?term=File&x=&y= (315 words)

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