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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
<copyright>
<year>1996</year><year>2016</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
</legalnotice>
<title>snmpa_local_db</title>
<prepared></prepared>
<responsible></responsible>
<docno></docno>
<approved></approved>
<checked></checked>
<date></date>
<rev></rev>
<file>snmpa_local_db.xml</file>
</header>
<module>snmpa_local_db</module>
<modulesummary>The SNMP built-in database</modulesummary>
<description>
<p>The module <c>snmpa_local_db</c> contains functions for
implementing tables (and variables) using the SNMP built-in
database. The database exists in two instances, one volatile
and one persistent. The volatile database is implemented with
ets. The persistent database is implemented with dets.
</p>
<p>There is a scaling problem with this database.
</p>
<list type="bulleted">
<item>Insertions and deletions are inefficient for large tables.
</item>
</list>
<p>This problem is best solved by using Mnesia instead.
</p>
<p>The following functions describe the interface to
<c>snmpa_local_db</c>. Each function has a Mnesia equivalent.
The argument <c>NameDb</c> is a tuple <c>{Name, Db}</c> where
<c>Name</c> is the symbolic name of the managed object (as defined
in the MIB), and <c>Db</c> is either <c>volatile</c> or
<c>persistent</c>. <c>mnesia</c> is not possible since all these
functions are <c>snmpa_local_db</c> specific.
</p>
</description>
<section>
<title>Common Data Types</title>
<p>In the functions defined below, the following types are
used:
</p>
<list type="bulleted">
<item>
<p><c>NameDb = {Name, Db}</c></p>
</item>
<item>
<p><c>Name = atom(), Db = volatile | persistent</c></p>
</item>
<item>
<p><c>RowIndex = [int()]</c></p>
</item>
<item>
<p><c>Cols = [Col] | [{Col, Value}], Col = int(), Value = term()</c></p>
</item>
</list>
<p>where <c>RowIndex</c> denotes the last part of the OID, that
specifies the index of the row in the table. <c>Cols</c> is a
list of column numbers in case of a get operation, and a list of
column numbers and values in case of a set operation.
</p>
</section>
<funcs>
<func>
<name>dump() -> ok | {error, Reason}</name>
<fsummary>Dump the database to disk</fsummary>
<type>
<v>Reason = term()</v>
</type>
<desc>
<p>This function can be used to manually dump the database
to file.</p>
</desc>
</func>
<func>
<name>match(NameDb, Pattern)</name>
<fsummary>Perform a match on the table</fsummary>
<desc>
<p>Performs an ets/dets matching on the table.
See Stdlib documentation, module ets, for a description of
<c>Pattern</c> and the return values.</p>
</desc>
</func>
<func>
<name>print()</name>
<name>print(TableName)</name>
<name>print(TableName, Db)</name>
<fsummary>Print the database to screen</fsummary>
<type>
<v>TableName = atom()</v>
</type>
<desc>
<p>Prints the contents of the database on
screen. This is useful for debugging since the
<c>STANDARD-MIB</c> and <c>OTP-SNMPEA-MIB</c>
(and maybe your own MIBs) are stored in <c>snmpa_local_db</c>.
</p>
<p><c>TableName</c> is an atom for a table in the database.
When no name is supplied, the whole database is shown.</p>
</desc>
</func>
<func>
<name>table_create(NameDb) -> bool()</name>
<fsummary>Create a table</fsummary>
<desc>
<p>Creates a table. If the table already exist, the old copy
is destroyed.
</p>
<p>Returns <c>false</c> if the <c>NameDb</c> argument is
incorrectly specified, <c>true</c> otherwise.</p>
</desc>
</func>
<func>
<name>table_create_row(NameDb, RowIndex, Row) -> bool()</name>
<fsummary>Create a row in a table</fsummary>
<type>
<v>Row = {Val1, Val2, ..., ValN}</v>
<v>Val1 = Val2 = ... = ValN = term()</v>
</type>
<desc>
<p>Creates a row in a table. <c>Row</c> is a tuple with
values for all columns, including the index columns.</p>
</desc>
</func>
<func>
<name>table_delete(NameDb) -> void()</name>
<fsummary>Delete a table</fsummary>
<desc>
<p>Deletes a table.</p>
</desc>
</func>
<func>
<name>table_delete_row(NameDb, RowIndex) -> bool()</name>
<fsummary>Delete the row in the table</fsummary>
<desc>
<p>Deletes the row in the table.</p>
</desc>
</func>
<func>
<name>table_exists(NameDb) -> bool()</name>
<fsummary>Check if a table exists</fsummary>
<desc>
<p>Checks if a table exists.</p>
</desc>
</func>
<func>
<name>table_get_row(NameDb, RowIndex) -> Row | undefined</name>
<fsummary>Get a row from the table</fsummary>
<type>
<v>Row = {Val1, Val2, ..., ValN}</v>
<v>Val1 = Val2 = ... = ValN = term()</v>
</type>
<desc>
<p><c>Row</c> is a tuple with values for all columns,
including the index columns.</p>
</desc>
</func>
</funcs>
<section>
<title>See Also</title>
<p>ets(3), dets(3), snmp_generic(3)
</p>
</section>
</erlref>
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