Better than icopy
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If caching problems occur but the copy is otherwise successful and PREFERRED was specified, then the copy is registered as a SHRLEVEL CHANGE copy. SHRLEVEL CONCURRENT copies are registered in SYSIBM.SYSCOPY as SHRLEVEL REFERENCE copies if no caching errors are experienced. Use REQUIRED to tell BMC AMI Copy to terminate the copy in this situation use PREFERRED (the default) to tell BMC AMI Copy to continue processing using SHRLEVEL CHANGE. You can use the keyword REQUIRED or PREFERRED after SHRLEVEL CONCURRENT to tell BMC AMI Copy what action to take when a consistent point cannot be obtained or maintained.
#BETTER THAN ICOPY CODE#
You must code SHRLEVEL CONCURRENT and RESETMOD NO in your BMC AMI Copy syntax to make Snapshot Copies.
#BETTER THAN ICOPY UPGRADE#
See the SNAPSHOT UPGRADE FEATURE for DB2 documentation for management set and authorization information. After installation, you must create the appropriate management set and configuration for the SNAPSHOT UPGRADE FEATURE and have the appropriate authorizations. To make the Snapshot feature available, you must have either XBM version 1.2.01 (or later) or the SNAPSHOT UPGRADE FEATURE (SUF) version 2.2.02 (or later) installed. This provides you with the ability to recover those spaces to the same, consistent point in time should a recovery of that group become necessary. You can use the Snapshot feature to make image copies of a group of Db2 table spaces to the same point of consistency while updates are in progress.
#BETTER THAN ICOPY FULL#
This technique requires only the most recent full copy and the last incremental copy for recovery. To reduce media usage when using incremental copies, you can make merged incremental copies using the CUMULATIVE YES option. For more information, see Optimizing the elapsed time for an incremental copy. This ensures that your incremental copies will never run longer than a full copy (which can happen when using random I/O to locate changed pages).
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We recommend READTYPE FULLSCAN for making incremental copies where the full copy was made using RESETMOD NO. This technique is very useful when you cannot tolerate putting the table space in STOP status when making a full copy. To give you a measure of control over the process when making incremental copies, BMC AMI Copy now provides the READTYPE option which allows you to specify sequential I/O or random I/O or to specify that BMC AMI Copy make the decision. When you anticipate a large or variable amount of updates to a table space occurring between full copies, using the FULL AUTO or CHANGELIMIT syntax option allows you to specify that a request for an incremental copy be escalated to a full copy request when the number of changed pages reaches a specified percentage.įor more information, see Escalating incremental copies to full copies. The following figure shows a typical comparison of the impact of using various incremental copy and full copy techniques on elapsed time for a range of changed page percentages.Ĭomparison of performance for different copy types However, using the BMC AMI Copy READTYPE FULLSCAN option for your incremental copies ensures that those copies will never run longer than a full copy. Incremental image copies that use random I/O can incur significant overhead reading the Db2 table space because of rotational delays and seeks. Under these circumstances, a full image copy runs almost as fast as an incremental image copy, and running a full copy might be the better choice because the BMC AMI Recover (or the IBM Db2 RECOVER) utility might run faster.įull image copies use sequential I/O and read and write many pages at a time. For example, in one case, only 2 percent of the rows changed, but these rows were located across 33 percent of the pages. Even when a small number of rows change, this might change a substantial percentage of pages, since there are typically many rows per page. However, the runtime of an incremental copy using random I/O increases as the percentage of changed pages increases. If only a few pages have changed, an incremental image copy runs much faster than a full image copy.
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Whether you use the Instant Snapshot capabilityįull image copy versus incremental image copy Whether you use the standard Snapshot Copy feature Which technique you use to make incremental copies Whether you make a full image copy or an incremental image copy The following items significantly affect the performance of BMC AMI Copy: