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The FairCom DB database engine optionally maintains a list of data files and the number of bytes of data cache to be primed at file open. When priming cache, FairCom DB reads the specified number of bytes for the given data file into data cache when physically opening the data file.
Data files are added to the priming list with configuration entries of the form:
PRIME_CACHE <data file name>#<bytes primed>
The <bytes primed> parameter accepts scaling factors (for example 2GB).
Example: The following keyword instructs the Server to read the first 100,000 bytes of data records from customer.dat into the data cache at file open:
PRIME_CACHE customer.dat#100000
A dedicated thread performs cache priming, permitting the file open call to return without waiting for the priming to be completed.
Use PRIME_CACHE with the SPECIAL_CACHE_FILE keyword to load dedicated cache pages at file open.
To prime index files, use configuration entries of the form:
PRIME_INDEX <index file name>#<bytes primed>[#<member no>]
If the optional <member no> is omitted, all index members are primed. If an index member number is specified, only that member is primed.
For example, the following keyword instructs the Server to read the first 100,000 bytes of index nodes in customer.idx into the index buffer space at file open:
PRIME_INDEX customer.idx#100000
The nodes are read first for the host index, and then for each member until the entire index is primed or the specified number of bytes has been primed.
The following example restricts the priming to the first member (the index after the host index):
PRIME_INDEX customer.idx#100000#1
The <data file name> or <index file name> can be a wild card specification using a ‘?’ for a single character and a ‘*’ for zero or more characters.
FairCom DB also supports priming the data cache in forward AND reverse order by index.
PRIME_CACHE_BY_KEY <data_file_name>#<data_record_bytes_to_prime>#<index_number>
For example
PRIME_CACHE_BY_KEY mark.dat#100000000#-1
Primes up to 100,000,000 bytes from mark.dat reading by the first index in reverse key order.
To use the prime cache file list for a bound server, use ctFILELIST() calls of the following form, where filename points to the file name, bytes is a LONG holding the number of bytes of index buffers to prime at file open, and member is a LONG holding the index member number. A negative value for member indicates the entire index.
ctFILELIST(filename,&bytes,ctPRICACHElist,ctADDfilelist);
ctFILELIST(filename,&bytes,&member,ctPRIINDEXlist,ctADDfilelist);
This function must be called prior to the opening of the file for which the cache is to be primed. The cache priming is performed by a dedicated thread launched by the Server at the end of the file open. This permits the open to return without waiting for the priming to be accomplished.
