RowStatus

class ydk.models.cisco_ios_xe.SNMPv2_TC.RowStatus

RowStatus (Enum Class)

The RowStatus textual convention is used to manage the

creation and deletion of conceptual rows, and is used as the

value of the SYNTAX clause for the status column of a

conceptual row (as described in Section 7.7.1 of [2].)

The status column has six defined values:

- `active’, which indicates that the conceptual row is

available for use by the managed device;

- `notInService’, which indicates that the conceptual

row exists in the agent, but is unavailable for use by

the managed device (see NOTE below);

- `notReady’, which indicates that the conceptual row

exists in the agent, but is missing information

necessary in order to be available for use by the

managed device;

- `createAndGo’, which is supplied by a management

station wishing to create a new instance of a

conceptual row and to have its status automatically set

to active, making it available for use by the managed

device;

- `createAndWait’, which is supplied by a management

station wishing to create a new instance of a

conceptual row (but not make it available for use by

the managed device); and,

- `destroy’, which is supplied by a management station

wishing to delete all of the instances associated with

an existing conceptual row.

Whereas five of the six values (all except `notReady’) may

be specified in a management protocol set operation, only

three values will be returned in response to a management

protocol retrieval operation: `notReady’, `notInService’ or

`active’. That is, when queried, an existing conceptual row

has only three states: it is either available for use by

the managed device (the status column has value `active’);

it is not available for use by the managed device, though

the agent has sufficient information to make it so (the

status column has value `notInService’); or, it is not

available for use by the managed device, and an attempt to

make it so would fail because the agent has insufficient

information (the state column has value `notReady’).

NOTE WELL

This textual convention may be used for a MIB table,

irrespective of whether the values of that table’s

conceptual rows are able to be modified while it is

active, or whether its conceptual rows must be taken

out of service in order to be modified. That is, it is

the responsibility of the DESCRIPTION clause of the

status column to specify whether the status column must

not be `active’ in order for the value of some other

column of the same conceptual row to be modified. If

such a specification is made, affected columns may be

changed by an SNMP set PDU if the RowStatus would not

be equal to `active’ either immediately before or after

processing the PDU. In other words, if the PDU also

contained a varbind that would change the RowStatus

value, the column in question may be changed if the

RowStatus was not equal to `active’ as the PDU was

received, or if the varbind sets the status to a value

other than ‘active’.

Also note that whenever any elements of a row exist, the

RowStatus column must also exist.

To summarize the effect of having a conceptual row with a

status column having a SYNTAX clause value of RowStatus,

consider the following state diagram:

STATE

+————–+———–+————-+————-

| A | B | C | D

| |status col.|status column|

|status column | is | is |status column

ACTION |does not exist| notReady | notInService| is active

————–+————–+———–+————-+————-

set status |noError ->D|inconsist- |inconsistent-|inconsistent-

column to | or | entValue| Value| Value

createAndGo |inconsistent- | | |

| Value| | |

————–+————–+———–+————-+————-

set status |noError see 1|inconsist- |inconsistent-|inconsistent-

column to | or | entValue| Value| Value

createAndWait |wrongValue | | |

————–+————–+———–+————-+————-

set status |inconsistent- |inconsist- |noError |noError

column to | Value| entValue| |

active | | | |

| | or | |

| | | |

| |see 2 ->D| ->D| ->D

————–+————–+———–+————-+————-

set status |inconsistent- |inconsist- |noError |noError ->C

column to | Value| entValue| |

notInService | | | |

| | or | | or

| | | |

| |see 3 ->C| ->C|wrongValue

————–+————–+———–+————-+————-

set status |noError |noError |noError |noError

column to | | | |

destroy | ->A| ->A| ->A| ->A

————–+————–+———–+————-+————-

set any other |see 4 |noError |noError |see 5

column to some| | | |

value | | see 1| ->C| ->D

————–+————–+———–+————-+————-

  1. goto B or C, depending on information available to the

agent.

  1. if other variable bindings included in the same PDU,

provide values for all columns which are missing but

required, then return noError and goto D.

  1. if other variable bindings included in the same PDU,

provide values for all columns which are missing but

required, then return noError and goto C.

  1. at the discretion of the agent, the return value may be

either:

inconsistentName: because the agent does not choose to

create such an instance when the corresponding

RowStatus instance does not exist, or

inconsistentValue: if the supplied value is

inconsistent with the state of some other MIB object’s

value, or

noError: because the agent chooses to create the

instance.

If noError is returned, then the instance of the status

column must also be created, and the new state is B or C,

depending on the information available to the agent. If

inconsistentName or inconsistentValue is returned, the row

remains in state A.

  1. depending on the MIB definition for the column/table,

either noError or inconsistentValue may be returned.

NOTE: Other processing of the set request may result in a

response other than noError being returned, e.g.,

wrongValue, noCreation, etc.

Conceptual Row Creation

There are four potential interactions when creating a

conceptual row: selecting an instance-identifier which is

not in use; creating the conceptual row; initializing any

objects for which the agent does not supply a default; and,

making the conceptual row available for use by the managed

device.

Interaction 1: Selecting an Instance-Identifier

The algorithm used to select an instance-identifier varies

for each conceptual row. In some cases, the instance-

identifier is semantically significant, e.g., the

destination address of a route, and a management station

selects the instance-identifier according to the semantics.

In other cases, the instance-identifier is used solely to

distinguish conceptual rows, and a management station

without specific knowledge of the conceptual row might

examine the instances present in order to determine an

unused instance-identifier. (This approach may be used, but

it is often highly sub-optimal; however, it is also a

questionable practice for a naive management station to

attempt conceptual row creation.)

Alternately, the MIB module which defines the conceptual row

might provide one or more objects which provide assistance

in determining an unused instance-identifier. For example,

if the conceptual row is indexed by an integer-value, then

an object having an integer-valued SYNTAX clause might be

defined for such a purpose, allowing a management station to

issue a management protocol retrieval operation. In order

to avoid unnecessary collisions between competing management

stations, `adjacent’ retrievals of this object should be

different.

Finally, the management station could select a pseudo-random

number to use as the index. In the event that this index

was already in use and an inconsistentValue was returned in

response to the management protocol set operation, the

management station should simply select a new pseudo-random

number and retry the operation.

A MIB designer should choose between the two latter

algorithms based on the size of the table (and therefore the

efficiency of each algorithm). For tables in which a large

number of entries are expected, it is recommended that a MIB

object be defined that returns an acceptable index for

creation. For tables with small numbers of entries, it is

recommended that the latter pseudo-random index mechanism be

used.

Interaction 2: Creating the Conceptual Row

Once an unused instance-identifier has been selected, the

management station determines if it wishes to create and

activate the conceptual row in one transaction or in a

negotiated set of interactions.

Interaction 2a: Creating and Activating the Conceptual Row

The management station must first determine the column

requirements, i.e., it must determine those columns for

which it must or must not provide values. Depending on the

complexity of the table and the management station’s

knowledge of the agent’s capabilities, this determination

can be made locally by the management station. Alternately,

the management station issues a management protocol get

operation to examine all columns in the conceptual row that

it wishes to create. In response, for each column, there

are three possible outcomes:

- a value is returned, indicating that some other

management station has already created this conceptual

row. We return to interaction 1.

- the exception `noSuchInstance’ is returned,

indicating that the agent implements the object-type

associated with this column, and that this column in at

least one conceptual row would be accessible in the MIB

view used by the retrieval were it to exist. For those

columns to which the agent provides read-create access,

the `noSuchInstance’ exception tells the management

station that it should supply a value for this column

when the conceptual row is to be created.

- the exception `noSuchObject’ is returned, indicating

that the agent does not implement the object-type

associated with this column or that there is no

conceptual row for which this column would be

accessible in the MIB view used by the retrieval. As

such, the management station can not issue any

management protocol set operations to create an

instance of this column.

Once the column requirements have been determined, a

management protocol set operation is accordingly issued.

This operation also sets the new instance of the status

column to `createAndGo’.

When the agent processes the set operation, it verifies that

it has sufficient information to make the conceptual row

available for use by the managed device. The information

available to the agent is provided by two sources: the

management protocol set operation which creates the

conceptual row, and, implementation-specific defaults

supplied by the agent (note that an agent must provide

implementation-specific defaults for at least those objects

which it implements as read-only). If there is sufficient

information available, then the conceptual row is created, a

`noError’ response is returned, the status column is set to

`active’, and no further interactions are necessary (i.e.,

interactions 3 and 4 are skipped). If there is insufficient

information, then the conceptual row is not created, and the

set operation fails with an error of `inconsistentValue’.

On this error, the management station can issue a management

protocol retrieval operation to determine if this was

because it failed to specify a value for a required column,

or, because the selected instance of the status column

already existed. In the latter case, we return to

interaction 1. In the former case, the management station

can re-issue the set operation with the additional

information, or begin interaction 2 again using

`createAndWait’ in order to negotiate creation of the

conceptual row.

NOTE WELL

Regardless of the method used to determine the column

requirements, it is possible that the management

station might deem a column necessary when, in fact,

the agent will not allow that particular columnar

instance to be created or written. In this case, the

management protocol set operation will fail with an

error such as `noCreation’ or `notWritable’. In this

case, the management station decides whether it needs

to be able to set a value for that particular columnar

instance. If not, the management station re-issues the

management protocol set operation, but without setting

a value for that particular columnar instance;

otherwise, the management station aborts the row

creation algorithm.

Interaction 2b: Negotiating the Creation of the Conceptual

Row

The management station issues a management protocol set

operation which sets the desired instance of the status

column to `createAndWait’. If the agent is unwilling to

process a request of this sort, the set operation fails with

an error of `wrongValue’. (As a consequence, such an agent

must be prepared to accept a single management protocol set

operation, i.e., interaction 2a above, containing all of the

columns indicated by its column requirements.) Otherwise,

the conceptual row is created, a `noError’ response is

returned, and the status column is immediately set to either

`notInService’ or `notReady’, depending on whether it has

sufficient information to make the conceptual row available

for use by the managed device. If there is sufficient

information available, then the status column is set to

`notInService’; otherwise, if there is insufficient

information, then the status column is set to `notReady’.

Regardless, we proceed to interaction 3.

Interaction 3: Initializing non-defaulted Objects

The management station must now determine the column

requirements. It issues a management protocol get operation

to examine all columns in the created conceptual row. In

the response, for each column, there are three possible

outcomes:

- a value is returned, indicating that the agent

implements the object-type associated with this column

and had sufficient information to provide a value. For

those columns to which the agent provides read-create

access (and for which the agent allows their values to

be changed after their creation), a value return tells

the management station that it may issue additional

management protocol set operations, if it desires, in

order to change the value associated with this column.

- the exception `noSuchInstance’ is returned,

indicating that the agent implements the object-type

associated with this column, and that this column in at

least one conceptual row would be accessible in the MIB

view used by the retrieval were it to exist. However,

the agent does not have sufficient information to

provide a value, and until a value is provided, the

conceptual row may not be made available for use by the

managed device. For those columns to which the agent

provides read-create access, the `noSuchInstance’

exception tells the management station that it must

issue additional management protocol set operations, in

order to provide a value associated with this column.

- the exception `noSuchObject’ is returned, indicating

that the agent does not implement the object-type

associated with this column or that there is no

conceptual row for which this column would be

accessible in the MIB view used by the retrieval. As

such, the management station can not issue any

management protocol set operations to create an

instance of this column.

If the value associated with the status column is

`notReady’, then the management station must first deal with

all `noSuchInstance’ columns, if any. Having done so, the

value of the status column becomes `notInService’, and we

proceed to interaction 4.

Interaction 4: Making the Conceptual Row Available

Once the management station is satisfied with the values

associated with the columns of the conceptual row, it issues

a management protocol set operation to set the status column

to `active’. If the agent has sufficient information to

make the conceptual row available for use by the managed

device, the management protocol set operation succeeds (a

`noError’ response is returned). Otherwise, the management

protocol set operation fails with an error of

`inconsistentValue’.

NOTE WELL

A conceptual row having a status column with value

`notInService’ or `notReady’ is unavailable to the

managed device. As such, it is possible for the

managed device to create its own instances during the

time between the management protocol set operation

which sets the status column to `createAndWait’ and the

management protocol set operation which sets the status

column to `active’. In this case, when the management

protocol set operation is issued to set the status

column to `active’, the values held in the agent

supersede those used by the managed device.

If the management station is prevented from setting the

status column to `active’ (e.g., due to management station

or network failure) the conceptual row will be left in the

`notInService’ or `notReady’ state, consuming resources

indefinitely. The agent must detect conceptual rows that

have been in either state for an abnormally long period of

time and remove them. It is the responsibility of the

DESCRIPTION clause of the status column to indicate what an

abnormally long period of time would be. This period of

time should be long enough to allow for human response time

(including `think time’) between the creation of the

conceptual row and the setting of the status to `active’.

In the absense of such information in the DESCRIPTION

clause, it is suggested that this period be approximately 5

minutes in length. This removal action applies not only to

newly-created rows, but also to previously active rows which

are set to, and left in, the notInService state for a

prolonged period exceeding that which is considered normal

for such a conceptual row.

Conceptual Row Suspension

When a conceptual row is `active’, the management station

may issue a management protocol set operation which sets the

instance of the status column to `notInService’. If the

agent is unwilling to do so, the set operation fails with an

error of `wrongValue’. Otherwise, the conceptual row is

taken out of service, and a `noError’ response is returned.

It is the responsibility of the DESCRIPTION clause of the

status column to indicate under what circumstances the

status column should be taken out of service (e.g., in order

for the value of some other column of the same conceptual

row to be modified).

Conceptual Row Deletion

For deletion of conceptual rows, a management protocol set

operation is issued which sets the instance of the status

column to `destroy’. This request may be made regardless of

the current value of the status column (e.g., it is possible

to delete conceptual rows which are either `notReady’,

`notInService’ or `active’.) If the operation succeeds,

then all instances associated with the conceptual row are

immediately removed.

active = 1
notInService = 2
notReady = 3
createAndGo = 4
createAndWait = 5
destroy = 6