The most common page size used is 2KB, though some systems uses 4KB page.
If a table is designed without specifying extent sizes, Informix uses a default of 16 pages for the first and 8 pages for each subsequent extent. Extent sizing is done when the table is initially created.
If Informix is still online, you can get a new onconfig with:
onstat -c >onconfig
If Informix is offline, you can retrieve the settings from the database with:
oncheck -pP 1 1
INNER JOIN, LEFT / RIGHT OUTER JOIN, FULL OUTER JOIN, CROSS JOIN
A DBA can use directives mostly to change / test / evaluate the execution plan (costs / benefits) for a query, by forcing an index / change join order / etc.
Informix IDS provide following modes:-
Administrators use this mode to perform maintenance functions that do not require the execution of SQL and DDL statements. Only the administrator (user informix) can access the database server.
Administrators use this mode to perform any maintenance task, including tasks requiring the execution of SQL and DDL statements. Administrators can also perform all other functions available in Online mode. You can see the current database server mode by executing the onstat - utility from the command.
Informix Universal Server was the brand name given to the 9.X versions of the product; the upgrade from the Informix Dynamic Server (IDS) 7.X products, skipping the XPS 8.X release numbers. The 9.X server contained a number of functional advances (data type extensibility, DataBlades etc), as well as improvements to the storage manager and SQL processing. The most recent versions of the Informix line -- 10.X -- are an evolutionary progression over the 9.X engine.
If the DBA has a query inside a script / program that connects to an Informix instance through an ODBC connection, and running the query results in an error, then he can use the TRACE functionality, and return DBINFO(sqlca.sqlerrd[1,2]).
from command line# onmonitor ->Logical-Logs->Databases.
The database server uses a concept called key-value locking to lock the deleted row. When the database server deletes a row, key values in the indexes for the table are not removed immediately. Instead, each key value is marked as deleted, and a lock is placed on the key value. One of the most important uses for key-value locking is to assure that a unique key remains unique through the end of the traction that deleted it.
You may ask questions about Perl, DBI and DBD::Informix, but only if an IBM or Informix database is involved, somehow -- it is not a general forum for arbitrary questions about Perl. However, there are alternative forums that you should also use, described in the product.
The email@example.com mailing list is a bi-directional gateway to the comp.databases.informix (c.d.i) UseNet news group. Messages posted to the news group are forwarded by mail to subscribers of the mailing list; responses sent to the firstname.lastname@example.org email address are also posted to the news group; and the gateway manages to keep track of things so that postings do not repeat themselves. The mailing list is 'closed' in that you cannot post directly to the list unless you also subscribe to the list. However, you can always post to the news group instead; that is fully open and unmoderated.
By setting PDQ PRIORITY the DBA can change the query execution priority and increase the number of internal threads spawned by Informix to satisfy the query. Also, some memory allocation strategies differ upon setting PDQPRIORITY.
IBM released Informix
In Informix, the smallest unit containing data is the “page”. A continuous group of pages form an extent
A collection of informix processes in charge of:
An Informix instance is a single connection to shared memory. It is represented by one or more on init processes. When Informix is started or stopped, these processes appear and disappear. Informix used to use the term "server" when referring to an instance, hence the environment variable DBSERVERNAME.
We can use the SQLCA structure to get the ISAM Error.
sqlca.sqlerrd holds the ISAM error return code.
We can also use the rgetlmsg() and rgetmsg() library functions to obtain ISAM error message text.
Yes, you can start Informix in verbose mode:
oninit -v (this works on NT as well)
Informix will print everything that happens.
To close the verbose mode: start a second terminal session (UNIX) or command prompt (NT) and execute:
N.B. Don't close your terminal session (UNIX) or command prompt (NT) while in verbose mode. This will take Informix offline immediately.
A chunk is a physical portion of disk on which Informix stores its data. A chunk can be either a raw partition or a file system file. Informix suggests that a chunk's name be a symbolic link to the actual chunk. For example, if you are using /dev/rdsk/c6t0d0s1 as a chunk, you could create a symbolic link named /dev/informix/chunk1 that points to /dev/rdsk/c6t0d0s@That way, if there are ever any problems with that disk, you could replace the disk with another one and just change the symbolic link.
Light sc occur under the following conditions: The optimizer chooses a sequential scan of the table. The number of pages in the table is greater than the number of buffers in the buffer pool. The isolation level obtains no lock or a shared lock on the table: Dirty Read (including non logging databases) isolation level Repeatable Read isolation level if the table has a shared or exclusive lock Committed Read isolation if the table has a shared lock
foreground writes (FG) should always be zero. A foreground write is caused when a session needs to have a page from disk placed into the buffer pool, but there are no clean/free buffers available. In this case, the sqlexec thread will pick a page off the least recently used side of an LRU queue, write it out, and mark the page as clean. This process is time consuming for a session and should be avoided.
A light scan may occur when Informix internal optimizer decides that the best execution plan will be a sequential scan (bad query selectivity, lack of indexes…). In this case, if the optimizer further decides that the data set resulting from the query will not fit in the buffer pool, it will bypass it. The result is a light scan.
The “chunk” is a file containing informix database data (or a subset of that data). In can be a file on a internal disk (cooked file) or a raw device (from a SAN platform or internal disks/arrays).
Whenever Informix sqlexec process searches for a free / clear buffer in order to read a page from the disk into that buffer is called foreground write operation. The performance penalty appears when there are no free / clean buffers left, and sqlexec has to search for a less used buffer, write its content to disk, clean the buffer and reuse the buffer for a foreground write operation – having the disadvantage of NOT being asynchronous (as chunk writes/lru writes)
None; this is a news group! That is, there are no rules enforced by the software. There are periodically discussions on c.d.i about what should and should not be said. This is my FAQ, so it gets my spin on the rules that should be followed.
* Format: HTML postings are strongly discouraged; so are MIME postings. Both cause problems with many frequently used news readers. That me that attachments aren't encouraged either. Also, sending the same information twice, once in HTML and once in plain text, is downright wasteful.
Yes, but you need to install version 7.30 TC 6 or higher.
A binary large object, also known as a blob, is a collection of binary data stored as a single entity in a database management system. Informix invented an alternative backronym, Binary Large Object. Blobs are typically images, audio or other multimedia objects, though sometimes binary executable code is stored as a blob.
The Informix database management system was conceived and designed by Roger Sippl in the late 1970s. Informix was founded in 1980, went public in 1986, and for a period during the 1990s Informix was the second most popular database system, after Oracle.