NOHRSC Technology > NOHRSC GIS Applications > Miscellaneous

1999 June 16

AWIPS and Informix run-time libraries

>NOHRSC applications need Informix run-time libraries in order to execute. The location of these libraries on the executing machine is specified when the executable is compiled. In the past, these libraries had been located in /usr/informix, and compiled to use them. Since NOHRSC supports backwards compatibility (such as GDP-based systems), we ship out executables that use those /usr/informix libraries. On the new AWIPS systems, however, these libraries have moved to /opt/informix. Without any intervention, running these executables on AWIPS gives a run-time error since /usr/informix doesn't exist.

To allow these executables to run properly on AWIPS, create a symbolic link named "/usr/informix" that links to the /opt/informix directory.

NOHRSC applications will thus be able to find the run-time libraries and execute.

Moving the GISRS database

Since the GISRS database contains absolute filepaths, it is necessary to tread lightly when moving the database across machines. If the user wants to :

• Completely duplicate the database and file structure:

  1. Copy all data files to exactly the same paths on the new machine.
  2. Unload the entire database, along with dbschemas.
  3. Create the new database.
  4. Recreate the database structure using dbschemas, then load the database.

• Copy the database, but have files in a different path on the new machine:

  1. Archive all the GIS layers using the Data Administration toolbar's Archive utility.
  2. Copy the remaining file structures over to the new machine. Hydrographs will be among them.
  3. Unload the remaining database, along with the dbschemas.
  4. Edit the unloaded "hydrograph" table and modify the file pathnames with a global change to reflect any difference in the new pathname.
  5. Create the new database.
  6. Recreate the database structure using the dbschemas, then load the remaining tables.
  7. Restore the GIS layers using the Data Administration toolbar's Restore utility. The archiving utility will look at the new environment variables, and place the files and update the database accordingly.

1998 November 25

Buffered Logging use

The following is of no concern to RFCs running NOHRSC applications supported by GDP-based Informix servers. The following is of concern to only those RFCs who are (or who are contemplating) using AWIPS-hosted Informix servers.

The following is the NOHRSC's understanding of the AWIPS Informix client/server relationships:

"It has come to our attention that NOHRSC delivered applications whose databases are hosted by AWIPS Informix servers that were not properly installed.

Briefly, AWIPS consists of 2 independent servers: DS1 (the primary) and DS2 (the secondary, or backup). During normal operations, only DS1 is directly involved in database client/server relationships. Transactions with DS1 are duplicated on DS2. Hence, the dbspaces on DS1 and DS2 should be exact duplicates of one another.

We are told that database redundancy is facilitated by defining buffered logging when databases are created on AWIPS Informix servers. Buffered logging is established during database creation with the following SQL command:

It is our understanding that if buffered logging is not established when the GISRS database is created on the AWIPS Informix server, the DS2 server will not contain a backup copy of the GISRS database.

During normal operations, you will not notice a problem if buffered logging is not turned on. DS1 will serve NOHRSC applications normally. Its during non-normal conditions that problems will arise (i.e., upgrading Informix, DS1 failure, etc). If buffered logging is not turned on and operations require a transition from DS1 to DS2, the NOHRSC applications (and all other applications which do not involve buffered logging) will fail.

We suspect that buffered logging was not turned on at some of the RFCs using AWIPS Informix servers. Those RFCs noticed problems with IHABBS after the most recent PRC Informix upgrade. The problems are unpredictable in nature. They will vary from a complete failure due to the absence of a GISRS database to "flakey" performance associated with out-of-date records and tables. The out-of-date information is due to partial replication on DS2 during Informix administration activities. Similar inconsistencies can arise under circumstances other than Informix upgrades (i.e., when, for any reason, DS2 rather than DS1 is used as the Informix server).

For new IHABBS installations on AWIPS machines, we recommend that the GISRS database be established by the RFC representative most familiar with AWIPS database management. Guidance for the proper definition of a new Informix database can be found in the "AWIPS Manager's Manual" (and see above).

For old IHABBS installations which did not define buffered logging when the GISRS database was originally created we suggest conferring with the RFC representative most familiar with AWIPS database management. We suspect that the most secure approach at this point is to:

1. Make sure no NOHRSC applications are running.
2. Run dbschema to develop a schema of the GISRS database.
3. Unload all GISRS tables.
4. Drop all GISRS tables.
5. Drop the GISRS database.
6. Create a new GISRS database with buffered logging turned on. Guidance for the proper definition of a new Informix database can be found in the "AWIPS Manager's Manual" (and see above).
7. Execute the dbschema output to recreate the dropped tables.
8. Finally, reload the recreated tables using the load command.

Following the above procedure SHOULD ensure that: (a) a GISRS database with buffered logging turned on has been created, (b) the new GISRS database looks just like the old GISRS database, (c) a duplicate version of the GISRS database is on DS2, and (d) the continued duplication of the GISRS database on DS2."

1998 November 18

Additional comments from Jeff Zimmerman

"A little bit more information. According to PRC, the CREATE DATABASE statement will create the database on both DS1 and DS2. However, if the database is created without buffered logging, then any transactions/updates of the database on DS1 will not be logged and replicated on DS2.

What happened with the AWIPS 4.0.5 upgrade was that the system was swapped over to be running off of DS2, while the upgrade took place on DS1. Then, when they brought DS1 back, it was restored from DS2, not the level 0 archive. Since the database was created without buffered logging, any changes made to the db while on DS1 were not propagated to DS2. So, when the restoration from DS2 took place, they were restoring the database based on its structure when it was initially created.

We ran into similar circumstances prior to build 3 when the WHFS database was not doing transaction logging. If a site had to fail over to DS2, they ended up running off an old copy of the database that dated to the initial establishment of the db."

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