====== Removing Indexing Manually=====

^Published By^Date^Version^Knowledge Level^Keywords^
|Revelation Technologies|29 JUL 1990|2.X|INTERMEDIATE|INDEXING, INDEXES, MFS, REMOVING|

Sometimes you need to remove indexing from a file manually. This is usually
happens when you clear or delete the indexing file (!filename) explicitly,
which also deletes important control information. When you then try to
remove indexing from the file, the system returns an error message.

In order to remove indexing from a file manually, there are three steps to
be performed.

  * Update the volume directory (formerly known as the media map).
  * Delete the indexing file.
  * Update the individual dictionary records.

Each of these steps will be covered in turn.

==== Updating the Volume Directory ====

The volume directory maintains information about each file in a volume. Part
of that information is a list of Modifying Filing Systems (MFSs) associated
with the file. When a file has indexing on it, an MFS called SI.MFS is
placed on the file. This MFS must be removed.

To remove the MFS, follow these steps.

  * Log to the account SYSPROG. Volume directories can only be edited from SYSPROG.
  * Attach the volume directory for the volume containing the file. The volume directory is an Advanced Revelation file called REVMEDIA. For example, if the file is on a volume called SALES_DATA, the TCL command would be:<code>ATTACH SALES_DATA REVMEDIA</code>
  * Bring the proper volume directory record up in the editor. Each file on the volume has a record in the volume directory that is identified by a two-part key. The first part of the key is the filename, and the second part is the name of the account that the file is in. If the indexed file is the CUSTOMERS file in the account SALES, the TCL command would be:<code>EDIT REVMEDIA CUSTOMERS*SALES</code>
  * Edit line two of the volume directory entry to remove SI.MFS. If line two has just SI.MFS on it, you can delete it by pressing [Ctrl-X]. If there are other MFSs on the file, use the [Delete] key to delete SI.MFS and the trailing value mark, if any.
  * Press [F9] to save the change, then press [Esc] to exit the editor.

==== Deleting the Indexing File ====

If the indexing file (!filename, not !INDEXING) still exists, it must be
deleted. To delete the file, follow these steps:

  * Log to the account to which the file belongs. Continuing with the example above, you need to log to the SALES account. From level one of TCL you can enter this command:<code>LOGTO SALES</code>
  * Attach the volume that holds the file:<code>ATTACH SALES_DATA</code>
  * Delete the indexing file:<code>DELETEFILE !CUSTOMERS</code>

==== Updating the Dictionary ====

The indexing system maintains a variety of information in the dictionary
record of an indexed field. Depending on the type on indexing, different
information is maintained.

You will have to edit the dictionary record for each field in the file that
was indexed:

//Warning! Do not use [Ctrl-D] (delete a line) or press [Enter] while editing a dictionary record. This will alter the dictionary record, making it unusable.//

To edit a dictionary record, enter from TCL:

<code>
   EDIT DICT.FILENAME FIELDNAME
</code>

=== Btree Indexes ===

Field 6 of each dictionary record tells the system whether or not this field
has a Btree index. If there is a 1 in this field, the field has had a Btree
index installed. Change the 1 to a 0 and save the record.

=== Cross Reference Indexes ===

When a Cross Reference index is placed on a field, a symbolic field is
created to maintain the index. This field can be identified by the .XREF
extension.

Because this field is no longer required, it should be deleted. If a cross
reference index is placed on the field again, the symbolic field will be
recreated.

In addition, a field with a Cross Reference index has the name of the cross
reference symbolic in field 22 of the dictionary record. Position the cursor
on line 22 of the dictionary record, press [Ctrl-X], and save the record.

=== Relational Indexes ===

Relational indexes use several fields in the dictionary record to store
their control information.

In the record that serves as the target of the relational index, change the
1 on line 25, which tells the system that this field's data is protected, to
a 0. Line 24 contains the name of the relational index, which should be
cleared with [Ctrl-X].

To completely remove the Relational index, the dictionary of the source file
must also be edited. In that dictionary, the source field will have the name
of the related field on line 23. Remove the name with[Ctrl-X].

=== Final Steps ===

In Advanced Revelation 2.0 and higher, there are two other records in the
dictionary that should be deleted: %PROTECT.SPEC% and %FIELDS%. Delete these
fields after editing the indexed fields.

Reattach the file and the system will recreate these records, reflecting the
changes made to the dictionary.

At this point the file has had all indexing removed. Indexes can be
re-established as necessary.