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Recovering compressed indexes

NGT Recover provides native support for recovering copies of compressed indexes made by DB2 or NGT Copy. (NGT Copy provides native support for copying compressed indexes.)

Additionally, NGT Recover provides native support for

  • Backout recovery of compressed indexes

  • Recovery of encrypted compressed indexes

  • Recovery of cabinet copies of compressed indexes

  • Optimized merge recovery of compressed indexes

  • Rebuilding compressed indexes

Two methods are available to make copies of compressed indexes. Each method has advantages and disadvantages.

  • Make copies of compressed indexes by expanding them

    Both the DB2 COPY utility and NGT Copy can make copies of compressed indexes by reading the compressed indexes directly from disk and expanding them before writing the image copy. This method has the advantage that the copy is registered in SYSCOPY (and, in the case of NGT Copy, the copy is compatible with those produced by the DB2 COPY utility).

    Some disadvantages of this method are that it takes time to expand the pages and the resulting image copies are larger than necessary. Also, NGT Copy copy techniques, such as Instant Snapshot copies and Online Consistent Copies, are not supported. (NGT Copy will make unexpanded copies if you request an expanded copy.)

  • Make copies of compressed indexes without expanding them

    NGT Copy can make copies of the compressed indexes without expanding them. NGT Copy registers these copies in the BMCXCOPY table. This method has the advantages that making the copies is faster and the copies are smaller than when copies are made of expanded indexes. Also, all NGT Copy copy techniques, such as Instant Snapshots, Online Consistent Copy, encrypted copies, and cabinet copies, are supported.

    When you make copies of compressed indexes without expanding them, the copy is not compatible with the DB2 utilities and NGT Recover is required to use these copies for recovery.

NGT Recover supports both expanded and unexpanded copies of compressed indexes, and automatically determines the type of the copies that are available.

Note

When you use the OUTCOPY option in NGT Recover, copies of compressed indexes must be unexpanded.

When you use NGT Copy, the IXEXPAND option indicates which method you want to use to create copies of compressed indexes. Valid values are AUTO, YES, and NO. The default value is AUTO. IXEXPAND AUTO specifies that NGT Copy will make unexpanded copies of compressed indexes if you are running with a Recovery Management solution password (and consequently have NGT Recover to recover using the unexpanded copies). If you are not running Recovery Management, NGT Copy will make expanded copies for compatibility with IBM. IXEXPAND NO specifies that compressed index copies are unexpanded. IXEXPAND YES specifies that compressed index copies are expanded. For more information on the IXEXPAND option, see Next Generation Technology Copy for DB2 documentation .

Note

If you do not have the Recovery Management solution, but you do have the NGT Recover and NGT Copy products, you should consider changing the value of the NGT Copy IXEXPAND installation option to NO to achieve the benefits of copying the compressed indexes without expansion.


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