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  1. #1
    Join Date
    Mar 2007
    Posts
    45

    concurrency control with time stamping

    Hello everyone,

    I am working on time stamping and so far I have found it to be quite challenging and I am wondering if someone can help me.

    I have been working with this tutorial:

    Consider the unserializable schedule below. Apply time stamping.
    Code:
    T1                          T2
    
    read A                  
                             read B
    A=A+2           
    store A
    read B           
                             B=B*2
                             store B
    B=B+1
    store B
                             read A
                             A=A*5
                             store A
    
    This is what I have come up with:
    
    A    A    B    B        T1           T2          status
    rd   up  rd   up     
    
    t1                       read A                    ok
               t2                         read B       ok
    t1                       A=A+2                    ok
    t1   t1                 store A                   ok
               t1            read B                    ok  why would I not rollback here?
               t2                         B=B*2       ok
               t2   t2                   store B       no 
                                          rollback...........
    t1                       B=B+1                     ok
    t1   t1                 store B                    ok
    t2                                    read A        ok
    t2                                    A=A*5        ok
    t2   t2                              store A       ok
    I have a few other questions on procedures but I wanted to kinda get a feel on how I did with this tutorial first to see how much I understood it.

    thanks,

  2. #2
    Join Date
    Mar 2007
    Posts
    45
    I guess no one either dares to tackle time stamping or nobody understands my question?

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