Version 8.2.5
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Database Space Allocation Rules

When processing an add or update record command, the Adabas nucleus may need to allocate an additional extent to any of the following file components:

This document describes the rules used for the allocation.

Address Converter (AC)

The size of the address converter is initially defined by the MAXISN parameter in the ADALOD utility. The actual highest expected ISN is slightly higher because the address converter is stored in entire blocks. For example:

If the Adabas nucleus requires an additional extent for a file when executing N1 commands, the allocation routine attempts to locate a new extent of 25% of the current size:

Normal Index (NI), Upper Index (UI), Data Storage (DS)

For the purpose of allocating a new extent, the following formulas are used:

graphics/ni_ui_ds.png

where

B number of blocks currently allocated.
E highest ISN expected.
U highest ISN currently allocated.

If an extent found in the FST is contiguous with the end of a previous extent, it is allocated for a maximum of Z blocks.

If no such extent can be found in the FST

Additionally, if the MAXNI, MAXUI, or MAXDS parameter is specified for the current file, the nucleus allocates no more than the specified maximum number of blocks for the NI, UI, or DS, respectively.

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