Fast file data retrieval?

[Virgil Stokes]

I have a rather large ASCII file that is structured as follows

header line
9 nonblank lines with alphanumeric data
header line
9 nonblank lines with alphanumeric data
...
...
...
header line
9 nonblank lines with alphanumeric data
EOF

where, a data set contains 10 lines (header + 9 nonblank) and there can 
be several thousand
data sets in a single file. In addition,*each header has a* *unique ID 
code*.

Is there a fast method for the retrieval of a data set from this large 
file given its ID code?

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