Data Services Newsletter

Volume 2 : No 2 : June 2000

COMBINE: A new synchronization tool

This year, we began a process of enabling network operators with the ability to quickly generate an accounting of DMC timeseries data holdings and provide the ability to compare this output with a similar file that is generated from the network operator’s database. The idea behind this is simply to resolve whether the DMC has complete data holdings from networks that ship data to the DMC for deep archiving. The files that are used in this analysis are called ‘synchronization’ files, and we have published the file format.

The DMC currently archives data from 96 different networks. As a result of many years of network operations and varying configurations, we have observed that uncertainty can arise about the status of our holdings when compared to what network operators think they have shipped to the DMC. We worked with the two Data Collection Centers, ASL and IDA, and implemented a new utility we call COMBINE (pronounced like the farm tool). By generating a synchronization file at a data center and ftp’ing this file to the DMC (, directory /pub/sync), you can use this file to compare your holdings to the timeseries information at the DMC. You can generate a sync file from the DMC database by using SeismiQuery (the DMC’s database interface); specifically the timeseries query – it offers “sync” file as an output option.

Combine screenshot
Figure 1: Screenshot of the Combine web utility

By default, a generated sync file is left on our web site in ~ftp/pub/sync/timeqc.### (where the ### field is the process ID associated with the file). This uniquely delimits your data information and allows users to compare two files. You can then plot graphically the data that is either missing from the DMC, or from the network that sent the data. There is also the option to view data common to both. We hope and expect that this utility will enable us to keep current in our data holdings, and enable network operators to verify that their data has been successfully archived at the DMC.

Example of Combine's Start Page
Figure 2: Example of Combine’s Start Page

by Rick Benson (IRIS Data Management Center)

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