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GISC core cache

GISC core cache

Inclusion of data in GISC core cache
The GISC core cache is defined by the keyword (flag) GlobalExchange

In order to ensure completeness of the Core Cache for GISCs:
1. The TT-GISC maintains the list of Core Cache data types, which are information flagged with “GlobalExchange” that all GISCs are required to have common holding (according to the Manual on WIS, and publishes the list through the WMO Secretariat.
2. The TT-GISC estimates the peak bandwidth used for the exchange of the Core Cache data by regular analysis of results from WIS Monitoring.
3. The TT-GISC coordinates and agrees on the minimum bandwidth required for each GISC to ensure the exchange of the Core Cache data.
4. Where TT-GISC cannot agree, or are unable to meet the expectatons of the data originator or user community, the decision will be escalated to the ITT-WIS for consideration of the President of CBS through Chair of OPAG-ISS.


Working practices

1. Daily data management is done without a decision of the TT-GISC.
(a). The TT-GISC publishes the data type list which the Core Cache data should include. The list should be clear enough that any new data is judged whether it’s included or not.
(b). When a WIS centre wishes to circulate new information through WIS, the centre may specifies the distribution scope “GlobalExchange” in the metadata, if the data type information corresponds to at least one of a type of Core Cache data type list.
(c). When a GISC receives information with metadata including the distribution scope keyword “GlobalExchange”, the GISC shall treat the information as Core Cache data.
(d). If a WIS centre submits a WIS metadata record which inappropriately has the keyword GlobalExchange, the principal GISC shall guide the WIS centre to an appropriate description.

2. Addition and deletion of Core Cache data type list requires a consensus of TT-GISC.
It was recommended in TT-GISC. In order to keep a history of Core Cache evolution requests, the TT-GISC should provide a template form to be filled with information (such as time input of the data and products, daily volume estimation …) by a WIS centre which wants to add new information in Core Cache.

3. The TT-GISC may add a data type in the following ranges.
This list materializes the definition of information intended for global exchange in the Manual on WIS 3.5.1 (time- and operation-critical information (data and products)). The list below only shows the maximum extent of the Core Cache, since it is not realistic to guarantee the global exchange of some of data, considering available bandwidth.
(a). Observation data that is specified in the Annex I to Resolution 40 (Cg-XII) (1) to (5)
(b). Observation data that is designated as the additional data according to the Resolution
(c). Products that are to be exchanged through the WIS in Manual on GDPFS (currently under development)

4. The first edition of the Core Cache data type list should be the minimal of necessity.
In order to ensure the stable operation, the list will be augmented within the bandwidth agreed at the TT-GISC. (e.g. (a) and (b) preceding paragraph) If some GISC cannot handle the data or there is a concern about the operation, addition will be deferred and will be proposed to the GISC to increase the bandwidth of the core network.

5. The TT-GISC may defer adding the data type which has concern about the communication bandwidth. NWP and Satellite data are examples at the moment.
As it is specified in the Manual on WIS, the Core Cache is required that the all GISCs have to exchange and cache it, and should be acceptable for all GISCs in terms of capacity, such as a server capacity and bandwidth of the core network. Thus it should be estimated to be able to pass through a circuit with the lowest bandwidth. It was recommended in TT-GISC.

6. The TT-GISC will regularly estimate the required bandwidth by analyzing the result from WIS monitoring. To create a mechanism of estimating the bandwidth required that is used for the Core Cache data exchange, GISC should monitor the bandwidth usage of the Core Cache data exchange. Even if a list of the data type is not changed, the demand for communication bandwidth changes over time. The TT-GISC will investigate the actual amount of data transferred in regular interval (e.g. every 3 months or every 6 months), and estimate the maximum communication bandwidth which is expected to be used for exchange of current data types. Separately, the TT-GISC will agree on a communication bandwidth that each GISC shall provide, and it may add data types only when the data congestion does not occur. (A possible criterion of non-congestion is that daily volume of traffic to be passed over any one circuit shall not exceed 80 per cent of its theoretical capacity in accordance with the Manual on GTS 1.3, Principle 4)

Escalation procedure Annex 2 to Rec. 36 (CBS-16)

1. Global Information System Centres’ representatives (i.e. TT-GISC) should, based on discussion with the providers (Data Collection or Production Centres and National Centres) and users, be the group to decide whether a data stream should go in or out of the 24 hour cache and be routinely distributed:
(a) That all GISCs have to maintain (e.g. GlobalExchange flag);
(b) That a number of GISCs have to maintain (e.g. RegionalExchange flag).

2. Normally, the decision to add a new or to remove an existing data stream will be by consensus of GISCs representatives in line with normal operational collaboration:
(a) An implementation time line will be a part of the decision;
(b) Decisions should be made in a short timescale (e.g. less than 2 weeks).

3. If unable to reach consensus or if the requester is not satisfied with the decision, the problem should be escalated to ITT-WIS:
(a) ITT-WIS should then make its recommendations based on information from requesters and GISCs;
(b) The president of CBS will make a decision based on the ITT-WIS recommendation, utilizing fast track procedures as appropriate.

Note that issues may be escalated by a GISC either in response to events, occurred or planned,
where it is anticipated it might impact on the functioning of WIS.