DELETE
Delete a record from an ISAM file
WTSupported in traditional Synergy on Windows
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WNSupported in Synergy .NET on Windows
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USupported on UNIX
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VSupported on OpenVMS
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DELETE(channel) [[error_list]]
Arguments
channel
The channel on which the ISAM file is open in update mode (U:I). (n)
error_list
(optional) An I/O error list. If any one of the specified errors occurs during the DELETE, control is transferred to the associated label.
Discussion
The DELETE statement deletes the current record on the specified channel. This statement is used exclusively with ISAM files on Windows and UNIX.
On OpenVMS, you can use DELETE to delete records from a relative file. You cannot use U:* if you want to delete records. You must open the file with an explicit submode (for example, U:I) to allow the DELETE to work.
You can use the DELETE statement only after a FIND, READ, or READS statement. The current record being deleted must be locked if the file can be accessed by other users; otherwise, you’ll get a “No current record” error ($ERR_NOCURR).
When deleting more than 10% of the data in a very large (greater than 100,000 records) multi-key ISAM file, you can improve performance when exclusive access is possible by writing out a sequential file of the data you want to save and using fconvert to reload and optimize the file. Note: If binary data is present (including RFAs or INTEGER, UNSIGNED, SEQUENCE, TIMESTAMP, and CTIMESTAMP keys), use a relative file instead of a sequential file. (For variable-length records with binary data present, see Synergy counted files.) |
Examples
.define TTCHN ,1 .define ISMCHN ,2 record rec data1 ,a30 key ,a16 data2 ,a25 record io ,a20 proc open(TTCHN, o,"tt:") display(TTCHN, "ISAM file to examine: ") reads(TTCHN, io, done) open(ISMCHN, u:i, io) repeat begin display(TTCHN, "Key: ") reads(TTCHN, io, done) read(ISMCHN, rec, io) writes(TTCHN, "Data: " + rec) display(TTCHN, "Delete this record? ") reads(TTCHN, io, done) if (io .eq. 'Y') delete(ISMCHN) end done, close ISMCHN stop end