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updated docs

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Jan Steemann 2014-07-04 13:53:24 +02:00
parent 772f5fc876
commit cf52748d39
2 changed files with 17 additions and 11 deletions
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25
Documentation/Books/Users/Transactions/Limitations.mdpp
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@ -7,18 +7,23 @@ and/or modification operations.
The implementation is not optimized for very long-running or very voluminous
operations, and may not be usable for these cases.
A major limitation is that a transaction must entirely fit into main
memory. This includes all data that is created, updated, or deleted during a
transaction, plus management overhead.
One limitation is that a transaction operation information must fit into main
memory. The transaction information consists of record pointers, revision numbers
and rollback information. The actual data modification operations of a transaction
are written to the write-ahead log and do not need to fit entirely into main
memory.
Transactions should thus be kept as small as possible, and big operations
should be split into multiple smaller transactions if they are too big to fit
into one transaction.
Ongoing transactions will also prevent the write-ahead logs from being fully
garbage-collected. Information in the write-ahead log files cannot be written
to collection data files or be discarded while transactions are ongoing.
Additionally, transactions in ArangoDB cannot be nested, i.e. a transaction
must not call any other transaction. If an attempt is made to call a transaction
from inside a running transaction, the server will throw error *1651 (nested
transactions detected)*.
To ensure progress of the write-ahead log garbage collection, transactions should
be kept as small as possible, and big transactions should be split into multiple
smaller transactions.
Transactions in ArangoDB cannot be nested, i.e. a transaction must not start another
transaction. If an attempt is made to call a transaction from inside a running
transaction, the server will throw error *1651 (nested transactions detected)*.
It is also disallowed to execute user transaction on some of ArangoDB's own system
collections. This shouldn't be a problem for regular usage as system collections will

3
Documentation/Books/Users/Transactions/README.mdpp
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@ -16,4 +16,5 @@ These *ACID* properties provide the following guarantees:
* Finally, the *durability* proposition makes sure that operations from
transactions that have committed will be made persistent. The amount of
transaction durability is configurable in ArangoDB, as is the durability
on collection level.
on collection level.