Re: Reading locked rows

In <1993Sep03.061326.21151@wvus.org> sford@wvus.org (Scott Ford) writes: >We're running online & istar 5.0 on a Sequent 2000 with ptx 2.0.4. We >talk to it using inet-pc 4.10 and powerbuilder running on windows. >Today's question #1 is about reading locked records. Here's the >scenario: > buffered logging data base "foo" with table "bozo". > table bozo has two columns "col1" (primary key) & "col2". > table foo also has row lock mode. >user 1 -> begin work; update bozo > set col2 = 10 > where col1 = 'a'; > let's say that the previous value for col2 was 5. note that > we HAVE NOT yet done a commit work. >user 2 -> set isolation to dirty read; > select * from bozo;> user 2 sees the row where col1 = a and shows col2 = 10 >user 3 -> set isolation to committed read; > select * from bozo;> user 3 errors (probably -244 or -246) due to locked record. I have a similar question/comment. I've written a standard simple little form -- It selects all the values from the table, puts them into a record and displays them on the screen. If a user selects the 'update' option, I begin a transaction set until the update is complete. Using the example Scott provided: user 1 -> begin work; update bozo let's say that the previous value for col2 was 5. A commit work hasn't been done yet. user 2 -> selects update option in program receives an error message that someone else is modifying the document. I thought this was the best way for the program to work -- Since we're working with a record, I lock the row when the user selects the 'update' option. However, I have a customer who is worried about concurrency. They are proposing that I move the commit work statement to just prior to the actual update. This means: user 1 -> update bozo the original value for col2 was 5. user 1 is changing it to 10, BUT we haven't started the transaction set yet. user 2 -> update bozo when user 2 selected the same row for update from bozo, user 2 sees the value for col 2 is 5 and changes it to 7 -- We still haven't started the transaction set. user 1 -> begin work and update col2=10 user 2 -> begin work and update col2=7 I'm curious which method others use... -- Clay Irving N2VKG | See the happy moron New York, New York | He doesn't give a damn. clay@panix.com (personal) | I wish I were a moron clay@garpac.com (work) | Oh God! Perhaps I am!