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Maximum file sizes - how to determine "key length"

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  • Maximum file sizes - how to determine "key length"

    Hello,

    The machine I'm looking at is V7R1

    Database file sizes states the following;
    Number of records contained in a file member 4 294 967 294 records2
    2 states the following;

    For files with keyed sequence access paths, the maximum number of records in a member varies and can be estimated using the following formulas.

    When ACCPTHSIZ(*MAX4GB) is specified, use the following formula:

    2,867,200,000
    10 + (.8 x key length)

    When ACCPTHSIZ(*MAX1TB) is specified, use the following formula:

    725,680,000,000
    12 + (.8 x key length)
    Here is an extract for DSPFD for my file;
    Code:
    Access path size  . . . . . . . . . . . . . : ACCPTHSIZ  *MAX1TB
    Access path logical page size . . . . . . . : PAGESIZE   *KEYLEN
    Maximum key length  . . . . . . . . . . . . :               29  
    Maximum record length . . . . . . . . . . . :              168
    Is maximum key length what they are referring to? Because using it in the afore mention forumla returns;

    725,680,000,000/ 12 + (0.8 * 29) = 20,615,909,090.91

    Which is 5x the stated initially stated value, I was expecting the result would be less than 4.295B.

    So is it genuinely the case that if you have sequenced access paths you can have more records? Or is "Maximum key length" the wrong value to use?

    Many Thanks,
    Ryan

  • #2
    Ryan,

    The Maximum number of records is limited by the RRN definition which is defined as an unsigned integer value. (4.29B) This limit is per file member/partition.

    I'm not sure of the conditions of when it could actually be less than the minimum IBM describes, but it can never be larger. The other limiting factor is the 1.7TB size limit per file.

    Jim

    Comment


    • #3
      Thanks Jim.

      Comment

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