Portal | Manuals | References | Downloads | Info | Programs | JCLs | Mainframe wiki | Quick Ref
IBM Mainframe Computers Forums Index
IBM Mainframe Computers Forums Index Mainframe: Search IBM Mainframe Forum: FAQ Memberlist Profile Log in to check your private messages Log in
dirty files in Vsam

Post new topic   Reply to topic    IBMMAINFRAMES.com Support Forums -> DFSORT/ICETOOL
View previous topic :: :: View next topic  
Author Message
subhash gowda
Warnings : 1

New User

Joined: 02 Jun 2005
Posts: 12

PostPosted: Thu Jun 02, 2005 3:40 pm    Post subject: dirty files in Vsam
Reply with quote

can any one clear my doubt, what does dirtyfiles mean
Back to top
View user's profile Send private message


Moderator Team Head

Joined: 26 Apr 2004
Posts: 4650
Location: Raleigh, NC, USA

PostPosted: Fri Jun 03, 2005 1:51 am    Post subject: Re: dirty files in Vsam
Reply with quote

Does this help (taken from a Google search)?:

Under native VSAM, physical updating occurs immediately as update requests are issued. If a transaction fails, its updates are backed out. Query applications may, on occasion, encounter a ?dirty read? showing the results of another transaction?s uncommitted updates. To eliminate dirty reads, the application must incur the overhead of ?consistent read? locking.

as well as this:

The "Dirty Read" Technique
The "dirty read" technique can be used to provide a high degree of concurrent access to VSAM files while avoiding the complications associated with CI and CA splits. The dirty read protocol can be summarized as follows:
The VSAM file must be defined with cross-region SHAREOPTIONS 4.
The file must be allocated with DISP=SHR.
All operations on the file, including reads, must be preceded with an ENQ for the data set. The data set name is specified for the ENQ "rname", but any string can be used for the ENQ "qname" (though it must be the same string for all accessors).
After a lock is obtained, the user's buffer must be refreshed with a GET request. This step also applies to new record insertions.
At the end of all file operations, the enqueue is released with a DEQ function call.
No lock is held during a wait (such as terminal input wait).
Before updating a previously read record, a fresh copy of the record must be obtained and compared to the original to ensure that no other user has updated the record while it was being browsed and modified. As always, the second read, the record comparison, and the update must be shielded by a lock.
Back to top
View user's profile Send private message
View previous topic :: :: View next topic  
Post new topic   Reply to topic    IBMMAINFRAMES.com Support Forums -> DFSORT/ICETOOL All times are GMT + 6 Hours
Page 1 of 1


Search our Forum:

Similar Topics
Topic Author Forum Replies Posted
No new posts VSAM RLS Wait time blayek JCL & VSAM 2 Mon Oct 02, 2017 9:05 pm
No new posts FTP Skip or ignore error and process ... AJAYREDDY All Other Mainframe Topics 3 Wed Sep 27, 2017 8:12 pm
No new posts Comparing 2 Files using Current time arunsoods SYNCSORT 9 Fri Sep 22, 2017 6:00 pm
No new posts Split 1 file into 10 output Files - S... Prasanth Kumar SYNCSORT 5 Sat Sep 16, 2017 12:02 am
No new posts Join records from 2 files with No Dup... Poha Eater DFSORT/ICETOOL 22 Sun Aug 27, 2017 10:35 pm

Back to Top
Job Vacancies | Forum Rules | Bookmarks | Subscriptions | FAQ | Polls | Contact Us