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AIX can be somewhat peculiar with regards to the way it does memory management. You can have a server with many multiples of gigabytes of RAM free, but still get out of memory or address space errors when running applications. One example is loading of extensions failing with unusual errors. For example, running as the owner of the PostgreSQL installation:

=# CREATE EXTENSION plperl;ERROR:  could not load library "/opt/dbs/pgsql/lib/plperl.so": A memory address is not in the address space for the process.

Running as a non-owner in the group possessing the PostgreSQL installation:

=# CREATE EXTENSION plperl;ERROR:  could not load library "/opt/dbs/pgsql/lib/plperl.so": Bad address

Another example is out of memory errors in the PostgreSQL server logs, with every memory allocation near or greater than 256 MB failing.

The overall cause of all these problems is the default bittedness and memory model used by the server process. By default, all binaries built on AIX are 32-bit. This does not depend upon hardware type or kernel in use. These 32-bit processes are limited to 4 GB of memory laid out in 256 MB segments using one of a few models. The default allows for less than 256 MB in the heap as it shares a single segment with the stack.

In the case of theplperl example, above, check your umask and the permissions of the binaries in your PostgreSQL installation. The binaries involved in that example were 32-bit and installed as mode 750 instead of 755. Due to the permissions being set in this fashion, only the owner or a member of the possessing group can load the library. Since it isn't world-readable, the loader places the object into the process' heap instead of the shared library segments where it would otherwise be placed.

The“ideal” solution for this is to use a 64-bit build of PostgreSQL, but that is not always practical, because systems with 32-bit processors can build, but not run, 64-bit binaries.

If a 32-bit binary is desired, setLDR_CNTRL toMAXDATA=0xn0000000, where 1 <= n <= 8, before starting the PostgreSQL server, and try different values andpostgresql.conf settings to find a configuration that works satisfactorily. This use ofLDR_CNTRL tells AIX that you want the server to haveMAXDATA bytes set aside for the heap, allocated in 256 MB segments. When you find a workable configuration,ldedit can be used to modify the binaries so that they default to using the desired heap size. PostgreSQL can also be rebuilt, passingconfigure LDFLAGS="-Wl,-bmaxdata:0xn0000000" to achieve the same effect.

For a 64-bit build, setOBJECT_MODE to 64 and passCC="gcc -maix64" andLDFLAGS="-Wl,-bbigtoc" toconfigure. (Options forxlc might differ.) If you omit the export ofOBJECT_MODE, your build may fail with linker errors. WhenOBJECT_MODE is set, it tells AIX's build utilities such asar,as, andld what type of objects to default to handling.

By default, overcommit of paging space can happen. While we have not seen this occur, AIX will kill processes when it runs out of memory and the overcommit is accessed. The closest to this that we have seen is fork failing because the system decided that there was not enough memory for another process. Like many other parts of AIX, the paging space allocation method and out-of-memory kill is configurable on a system- or process-wide basis if this becomes a problem.

• Set your path to use the Cygwin bin directory before the Windows utilities. This will help prevent problems with compilation.

• Theadduser command is not supported; use the appropriate user management application on Windows NT, 2000, or XP. Otherwise, skip this step.

• Thesu command is not supported; use ssh to simulate su on Windows NT, 2000, or XP. Otherwise, skip this step.

• OpenSSL is not supported.

• Startcygserver for shared memory support. To do this, enter the command/usr/sbin/cygserver &. This program needs to be running anytime you start the PostgreSQL server or initialize a database cluster (initdb). The defaultcygserver configuration may need to be changed (e.g., increaseSEMMNS) to prevent PostgreSQL from failing due to a lack of system resources.

• Building might fail on some systems where a locale other than C is in use. To fix this, set the locale to C by doingexport LANG=C.utf8 before building, and then setting it back to the previous setting after you have installed PostgreSQL.

• The parallel regression tests (make check) can generate spurious regression test failures due to overflowing thelisten() backlog queue which causes connection refused errors or hangs. You can limit the number of connections using the make variableMAX_CONNECTIONS thus:

  make MAX_CONNECTIONS=5 check

  (On some systems you can have up to about 10 simultaneous connections.)

If PostgreSQL on Windows crashes, it has the ability to generateminidumps that can be used to track down the cause for the crash, similar to core dumps on Unix. These dumps can be read using theWindows Debugger Tools or usingVisual Studio. To enable the generation of dumps on Windows, create a subdirectory namedcrashdumps inside the cluster data directory. The dumps will then be written into this directory with a unique name based on the identifier of the crashing process and the current time of the crash.

You can build with either GCC or Sun's compiler suite. For better code optimization, Sun's compiler is strongly recommended on the SPARC architecture. If you are using Sun's compiler, be careful not to select/usr/ucb/cc; use/opt/SUNWspro/bin/cc.

You can download Sun Studio fromhttps://www.oracle.com/technetwork/server-storage/solarisstudio/downloads/. Many GNU tools are integrated into Solaris 10, or they are present on the Solaris companion CD. If you need packages for older versions of Solaris, you can find these tools athttp://www.sunfreeware.com. If you prefer sources, look athttps://www.gnu.org/prep/ftp.

Ifconfigure complains about a failed test program, this is probably a case of the run-time linker being unable to find some library, probably libz, libreadline or some other non-standard library such as libssl. To point it to the right location, set theLDFLAGS environment variable on theconfigure command line, e.g.,

configure ... LDFLAGS="-R /usr/sfw/lib:/opt/sfw/lib:/usr/local/lib"

See theld man page for more information.

On the SPARC architecture, Sun Studio is strongly recommended for compilation. Try using the-xO5 optimization flag to generate significantly faster binaries. Do not use any flags that modify behavior of floating-point operations anderrno processing (e.g.,-fast).

If you do not have a reason to use 64-bit binaries on SPARC, prefer the 32-bit version. The 64-bit operations are slower and 64-bit binaries are slower than the 32-bit variants. On the other hand, 32-bit code on the AMD64 CPU family is not native, so 32-bit code is significantly slower on that CPU family.

Yes, using DTrace is possible. SeeSection 27.5 for further information.

If you see the linking of thepostgres executable abort with an error message like:

Undefined                       first referenced symbol                             in fileAbortTransaction                    utils/probes.oCommitTransaction                   utils/probes.old: fatal: Symbol referencing errors. No output written to postgrescollect2: ld returned 1 exit statusmake: *** [postgres] Error 1

your DTrace installation is too old to handle probes in static functions. You need Solaris 10u4 or newer to use DTrace.