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CHANGELIMIT

The CHANGELIMIT option specifies the boundaries for producing an incremental, full, or no copy based on the percentage of changed pages in the table space, partition, or data set.

CHANGELIMIT syntax diagram

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Important

Specifying CHANGELIMIT is the same as using FULL AUTO FULLPCT (FULL). Options specified with FULL AUTO can be specified with CHANGELIMIT, except FULLPCT, which is implied with CHANGELIMIT. If an incremental image copy is produced as a result of using CHANGELIMIT, CHECKTSLEVEL 2 is automatically adjusted to CHECKTSLEVEL 1. CHANGELIMIT is not valid for table spaces with the TRACKMOD NO attribute.

The CHANGELIMIT option and the FULL AUTO FULLPCT option are effectively the same and act on two values—incrPct and fullPct—to determine what type of copy to make. incrPct and fullPct are positional parameters. If a comma is used in the expression and incrPct is not specified, it defaults to the installation option INCRPCT value. If a comma is used and fullPct is not specified, it defaults to the installation option FULLPCT value. The default value of the INCRPCT installation option is 0. The default value of the FULLPCT installation option is 50.

You can also specify the value of incrPct and fullPct as the keyword ANY. You can use ANY to create an incremental or full copy if any pages are changed, instead of based on whether the percentage of changed pages falls within the specified range of values.

incrPct

Specifies a percent of changed pages used to determine whether to make an incremental copy or no copy. incrPct is optional. incrPct must be an integer or decimal value from 0 to 100. A decimal value can be specified to the hundredth’s place (1/100 of a percent). The decimal point is not required when specifying a whole integer.

In the option statement, CHANGELIMIT (incrPct, fullPct), you can specify incrPct as the keyword, ANY. If you use CHANGELIMIT (ANY, fullPct), BMC AMI Copy creates an incremental copy if any pages are changed, and the percentage of pages changed does not exceed the value of fullPct. If the percentage of pages changed equals or exceeds the value of fullPct, BMC AMI Copy creates a full copy.

fullPct

Specifies a percent of changed pages used to determine whether to make a full copy instead of an incremental copy. fullPct is required. fullPct must be an integer or decimal value from 0 to 100. A decimal value can be specified to the hundredth’s place (1/100 of a percent). The decimal point is not required when specifying a whole integer.

In the option statement, CHANGELIMIT ( fullPct), you can specify fullPct as the keyword, ANY. CHANGELIMIT ANY creates a full copy if any pages are changed.

CHANGELIMIT (incrPct, fullPct) or FULL AUTO FULLPCT (incrPct, fullPct) are evaluated as follows:

  • If percent changed pages is less than or equal to incrPct, (x <= incrPct), do not make a copy. 
  • If percent changed pages is greater than incrPct but less than fullPct, ( incrPct < x < fullPct), make an incremental copy.
    If the value of incrPct is specified as ANY (i.e. option statement CHANGELIMIT (ANY, fullPct) is used), make an incremental copy if any pages are changed, but the percentage of pages changed does not exceed fullPct.
  • If percent changed pages is greater than or equal to fullPct, (x >= fullPct), make a full copy.
    If the value of incrPct is specified as ANY (i.e. option statement CHANGELIMIT (ANY, fullPct) is used), make a full copy if any pages are changed, and the percentage of pages changed exceeds fullPct.

To bypass a copy for a table space with no changed pages, specify FULL AUTO or CHANGELIMIT (0, fullPct). In this case, BMC AMI Copy makes an incremental copy if any pages have changed or a full copy if the percentage of changed pages equals or exceeds fullPct. 

Important

An exception occurs when you specify incrPct as 0 and EMPTY NO, in which case BMC AMI Copy makes a copy even if there are no changed pages if BMC AMI Copy is able to acquire a registration point.

CHANGELIMIT ( incrPct,0) or FULL AUTO FULLPCT ( incrPct,0) allows you the flexibility to make an incremental copy or no copy at all based on changed pages. If the percent of changed pages is greater than incrPct, an incremental copy will be made unless other reasons cause escalation to a full copy. 0 prevents escalation to a full copy based on changed pages. Otherwise, no copy will be made.

FULL AUTO FULLPCT(.01) or CHANGELIMIT(.01) allows the flexibility to make a full copy or no copy based on changed pages. If any pages have changed since the last image copy, BMC AMI Copy will report a minimum of 0.01 percent changed pages and will make a full copy. Because BMC AMI Copy analyzes open log ranges to determine if any changes have been made since the last copy, RESETMOD YES is not required in this case. You can also use CHANGELIMIT ANY to create a full copy if any pages have changed.

Also, consider the following information when you use this option:

  • If the (incrPct, fullPct) format is used, it is possible that BMC AMI Copy will not make an image copy at all. Therefore, BMC AMI Copy will determine the percent of changed pages before QUIESCE processing to avoid dynamic allocation of the output data set. If the (fullPct) format is used, the estimate will occur after QUIESCE processing.
  • If you specified CHANGELIMIT (fullPct) or FULL AUTO FULLPCT (fullPct) and there are no changed pages, BMC AMI Copy will register an incremental copy only if you also specified the EMPTY NO option and BMC AMI Copy is able to acquire a registration point.
  • The parentheses around incrPct and fullPct are optional and are shown in the text above for clarity.
  • When two values are used with CHANGELIMIT or FULLPCT, which means that a copy might not be made, and you are using stacked tape for your copies, you must use dynamic allocation. Otherwise, the VOL=REF of a copy could refer to a previous copy data set that was not actually created if a copy was not made.

  • When CHANGELIMIT(incrPct,fullPct) is used with SHRLEVEL CONCURRENT and with GROUP YES specified or implied, only those spaces in the group with changed pages will be copied.

    See Specifying-conditional-image-copies for examples of its use. 

MAXINCRS integer

Specify MAXINCRS integer with FULL AUTO or CHANGELIMIT to tell BMC AMI Copy to escalate the request to a full image copy if the number of non-merged (CUMULATIVE NO) incremental copies made since the last full copy reaches integer. When calculating integer, BMC AMI Copy counts merged CUMULATIVE YES RESETMOD NO copies as one and each non-merged CUMULATIVE NO copy as one. Valid values of integer are 1 through 100. If you do not specify MAXINCRS, BMC AMI Copy uses the value of the MAXINCRS installation option. The default value of the MAXINCRS installation option is 6.

Refer to Escalation-due-to-limiting-the-number-of-incremental-copies for information about when to use this option.

Related topic

Global-COPY-options


 

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