AdagerHome Your Adager Guide (Section 6 of 13)
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Adager technology

Adager goes straight to the point
Adager directly updates the database's root file and the affected dataset files, without the need for a database reload.

Consolidation of tasks
Due to their exclusive nature, some Adager functions (such as chain fixing, dataset repacking, database copying or database renaming) take effect immediately.

Most other Adager functions get queued up and carried out in a single Adager pass that is carefully organized and sequenced to minimize total elapsed time.

Adager preprocess certification
As soon as Adager opens a database, it does an exhaustive preprocess consistency checking.

Some potential database inconsistencies that Adager discovers are so subtle that IMAGE itself may not catch them until it is too late and your applications, inconveniently, abort.

You may ask, "Why is Adager so paranoid?" and the answer is that IMAGE's privileged files and tables must be absolutely, positively consistent among themselves. Discrepancies—even subtle ones—almost always guarantee future problems.

There are various ways, malicious or innocent, to disrupt the tight coupling of IMAGE structures. For instance, we have seen cases where careless operators—whose operating-system capabilities exceeded their knowledge of delicate and privileged data structures—restored only certain datasets from a backup, thereby introducing catastrophic inconsistencies for the current production databases. We have also encountered files that were damaged because of hardware or system failures.

First, Adager checks the root file to make sure that it is self-consistent. Adager then checks the structures of all of the files corresponding to the database's datasets. Adager reports warnings (such as an automatic master dataset with no paths) and errors (such as a corrupted path table).

Adager provides a wealth of options to help you correct any discrepancies up-front, before they cause further damage. This is equivalent to checking a swimming pool to make sure it has water before you dive into it. If it happens to be empty (or dangerously low), Adager helps you "fill it up," if possible.

If everything looks reasonable after the preprocess certification, Adager lets you proceed.

In general, these up-front Adager cross checks give you a warm, fuzzy feeling that things are not obviously wrong with your database. But you have to be realistic: these global diagnostics limit themselves, by definition, to the big picture. They do not, for instance, detect broken chains within a dataset—you would use Examine Path for this purpose (see page 24 ).

In-depth diagnostics
Passing Adager's preprocess consistency checking does not guarantee that everything is perfect. On the other hand, failing Adager's preprocess certification almost always points to potential trouble and you should do a full database diagnostic as soon as possible.

A comprehensive Adager diagnostic, such as Examine Path, by its very nature and functionality, will take more time. But its recommendations will be more precise, down to the data-entry level (chain counts and pointers, search-field values, in-use bits, and so on).

Roll back
If Adager is unable to complete a change of capacity for a dataset (because of lack of disc space, for instance), it leaves the dataset unchanged if there is no corrective action on your part.

There are two ways for you to help Adager overcome environmental problems such as lack of disc space.

Renaming and simultaneously renumbering
Although the real power of Adager only becomes apparent when you specify amazingly complex database changes, you will appreciate the elegance with which Adager handles some tricky transformations, such as renaming and simultaneously shuffling (thereby renumbering) items and datasets.

Reviewing scheduled changes
Before deciding to apply your queued-up changes, you can review their ever-evolving current state with Adager's browsing functions.

AdagerHome Your Adager Guide (Section 6 of 13)
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