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18 lines
906 B
Markdown
18 lines
906 B
Markdown
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# Transaction at defined snapshot number
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With this feature it's possible to create parallel (via different attachments) processes reading consistent data from a database.
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For example, a backup process may create multiple threads paralleling reading data from the database.
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Or a web service may dispatch distributed sub services paralleling doing some processing.
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That is accomplished creating a transaction with `SET TRANSACTION SNAPSHOT [ AT NUMBER <snapshot number> ]` or `isc_tpb_at_snapshot_number <snapshot number length> <snapshot number>`.
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The `snapshot number` from the first transaction may be obtained with `RDB$GET_CONTEXT('SYSTEM', 'SNAPSHOT_NUMBER')` or transaction info call with `fb_info_tra_snapshot_number`.
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Note that the `snapshot number` passed to the new transaction must be a snapshot of an active transaction.
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Author:
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Adriano dos Santos Fernandes <adrianosf at gmail.com>
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