The EntireX Broker is a multithreaded application and communicates among multiple tasks in memory pools. If you do not need to restrict the memory expansion of EntireX Broker, we strongly recommend you enable the dynamic memory management in order to handle changing workload appropriately. See Dynamic Memory Management below. If dynamic memory management is disabled, non-expandable memory is allocated during startup to store all internal control blocks and the contents of messages.
This document covers the following topics:
Resource considerations apply to both the global and service-specific levels:
Dynamic assignment of global resources to services that need them prevents the return of a "Resource Shortage" code to an application when resources are available globally. It also enables the EntireX Broker to run with fewer total resources, although it does not guarantee the availability of a specific set of resources for a particular service.
Flow control ensures that individual services do not influence the behavior of other services by accident, error, or simply overload. This means that you can restrict the resource consumption of particular services in order to shield the other services.
In order to satisfy both global and service-specific requirements, the EntireX Broker allows you to allocate resources for each individual service or define global resources which are then allocated dynamically to any service that needs them.
The resources in question are the number of conversations, number of servers, plus units of work and the message storage, separated in a long buffer of 4096 bytes and short buffer of 256 bytes. These resources are typically the bottleneck in a system, especially when you consider that non-conversational communication is treated as the special case of "conversations with a single message only" within the EntireX Broker.
Global resources are defined by the parameters in the Broker section of the attribute file. The number of conversations allocated to each service is defined in the service-specific section of the attribute file. Because the conversations are shared by all servers that provide the service, a larger number of conversations should be allocated to services that are provided by more than one server. The number of conversations required is also affected by the number of clients accessing the service in parallel.
You can specify a set of global resources with no restrictions on which service allocates the resources:
Specify the global attributes with the desired values.
Do not specify any additional restrictions. That is, do not provide values for the following Broker-specific attributes:
LONG-BUFFER-DEFAULT
SHORT-BUFFER-DEFAULT
CONV-DEFAULT
SERVER-DEFAULT
Also, do not provide values for the following server-specific attributes:
LONG-BUFFER-LIMIT
SERVER-LIMIT
SHORT-BUFFER-LIMIT
CONV-LIMIT
The following example defines global resources. If no additional definitions are specified, resources are allocated and assigned to any server that needs them.
NUM-CONVERSATION=1000 NUM-LONG-BUFFER=200 NUM-SHORT-BUFFER=2000 NUM-SERVER=100
You can restrict resource allocation for particular services in advance:
Use CONV-LIMIT to limit the resource consumption for
a specific service.
Use CONV-DEFAULT to provide a default limit for
services for which CONV-LIMIT is not
defined.
In the following example, attributes are used to restrict resource allocation:
DEFAULTS=BROKER NUM-CONVERSATION=1000 CONV-DEFAULT=200 DEFAULTS=SERVICE CLASS=A, SERVER=A, SERVICE=A, CONV-LIMIT=100 CLASS=B, SERVER=B, SERVICE=B, CONV-LIMIT=UNLIM CLASS=C, SERVER=C, SERVICE=C
Memory for a total of 1000 conversions is allocated
(NUM-CONVERSATION=1000).
Service A (CLASS
A,SERVER A,SERVICE A) is limited to 100
conversation control blocks used simultaneously (CONV-LIMIT=100). The
application that wants to start more conversations than specified by the limit
policy will receive a "Resource shortage" return code. This return
code should result in a retry of the desired operation a little later, when the
resource situation may have changed.
Service B (CLASS
B,SERVER B,SERVICE B) is allowed to try to
allocate as many resources as necessary, provided the resources are available
and not occupied by other services. The number of conversations that may be
used by this service is unlimited (CONV-LIMIT
=UNLIM).
Service C (CLASS
C,SERVER C,SERVICE C) has no explicit value
for the CONV-LIMIT attribute. The number of
conversation control blocks that it is allowed to use is therefore limited to
the default value which is defined by the
CONV-DEFAULT Broker attribute.
The same scheme applies to the allocation of message buffers and servers:
In the following example, long message buffers are allocated using the
keywords NUM-LONG-BUFFER, LONG-BUFFER-DEFAULT
and LONG-BUFFER-LIMIT:
DEFAULTS=BROKER NUM-LONG-BUFFER=2000 LONG-BUFFER-DEFAULT=250 DEFAULTS=SERVICE CLASS=A, SERVER=A, SERVICE=A, LONG-BUFFER-LIMIT=100 CLASS=B, SERVER=B, SERVICE=B, LONG-BUFFER-LIMIT=UNLIM CLASS=C, SERVER=C, SERVICE=C
In the following example, short message buffers are allocated using the
keywords NUM-SHORT-BUFFER,
SHORT-BUFFER-DEFAULT and
SHORT-BUFFER-LIMIT:
DEFAULTS=BROKER NUM-SHORT-BUFFER=2000 SHORT-BUFFER-DEFAULT=250 DEFAULTS=SERVICE CLASS=A, SERVER=A, SERVICE=A, SHORT-BUFFER-LIMIT=100 CLASS=B, SERVER=B, SERVICE=B, SHORT-BUFFER-LIMIT=UNLIM CLASS=C, SERVER=C, SERVICE=C
In the following example, servers are allocated using the keywords
NUM-SERVER, SERVER-DEFAULT and
SERVER-LIMIT:
DEFAULTS=BROKER NUM-SERVER=2000 SERVER-DEFAULT=250 DEFAULTS=SERVICE CLASS=A, SERVER=A, SERVICE=A, SERVER-LIMIT=100 CLASS=B, SERVER=B, SERVICE=B, SERVER-LIMIT=UNLIM CLASS=C, SERVER=C, SERVICE=C
If privileged services (services with access to unlimited resources)
exist, specify "UNLIMITED" for the attributes
CONV-LIMIT, SERVER-LIMIT,
LONG-BUFFER-LIMIT and SHORT-BUFFER-LIMIT in
the service-specific section of the attribute file.
For example:
DEFAULTS=SERVICE CONV-LIMIT=UNLIM LONG-BUFFER-LIMIT=UNLIM SHORT-BUFFER-LIMIT=UNLIM SERVER-LIMIT=UNLIM
To ensure a resource reservoir for peak load of privileged services, define more resources than would normally be expected by specifying larger numbers for the Broker attributes that control global resources:
NUM-SERVER NUM-CONVERSATION CONV-DEFAULT LONG-BUFFER-DEFAULT SHORT-BUFFER-DEFAULT SERVER-DEFAULT
The maximum number of units of work (UOWs) that can be active concurrently is specified in the Broker attribute file. The MAX-UOWS attribute can be specified for the Broker globally as well as for individual services. It cannot be calculated automatically. If a service is intended to process UOWs, a MAX-UOWS value must be specified.
If message processing only is to be done, specify MAX-UOWS=0 (zero). The Broker (or the service) will not accept units of work, i.e., it will process only messages that are not part of a UOW. Zero is used as the default value for MAX-UOWS in order to prevent the sending of UOWs to services that are not intended to process them.
To ensure that each service runs without impacting other services, allow the EntireX Broker to calculate resource requirements automatically:
Ensure that the attributes that define the default total for the Broker and the limit for each service are not set to UNLIM.
Specify AUTO for the Broker attribute that defines the total number of the resource.
Specify a suitable value for the Broker attribute that defines the default number of the resource.
The total number required will be calculated from the number defined for each service. The resources that can be calculated this way are Number of Conversations, Number of Servers, Long Message Buffers and Short Message Buffers.
Avoid altering the service-specific definitions at runtime. Doing so
could corrupt the conversation consistency. Applications might receive a
message such as "NUM-CONVERSATIONS reached" although the addressed
service does not serve as many conversations as defined. The same applies to
the attributes that define the long and short buffer resources.
Automatic resource calculation has the additional advantage of limiting the amount of memory used to run the EntireX Broker. Over time, you should be able to determine which services need more resources by noting the occurrence of the return code "resource shortage, please retry". You can then increase the resources for these services. To avoid disruption to the user, you could instead allocate a relatively large set of resources initially and then decrease the values using information gained from the Administration Monitor application.
To calculate the total number of conversations automatically, ensure that
the CONV-DEFAULT Broker attribute and the
CONV-LIMIT service-specific attribute are not set to UNLIM
anywhere in the attribute file. Specify NUM-CONVERSATION=AUTO and an
appropriate value for the CONV-DEFAULT Broker
attribute. The total number of conversations will be calculated using the value
specified for each service.
For example:
DEFAULTS=BROKER NUM-CONVERSATION=AUTO CONV-DEFAULT=200 DEFAULTS=SERVICE CLASS=A, SERVER=A, SERVICE=A CLASS=B, SERVER=B, SERVICE=B, CONV-LIMIT=100 CLASS=C, SERVER=C, SERVICE=C
Service A and Service C both need 200 conversations (the default
value). Service B needs 100 conversations
(CONV-LIMIT=100).
Because NUM-CONVERSATIONS is defined as
AUTO, the broker calculates a total of 500 conversations (200 + 200 + 100).
NUM-CONVERSATIONS=AUTO allows the number
of conversations to be flexible without requiring additional specifications. It
also ensures that the broker is started with enough resources to meet all
the demands of the individual services.
"AUTO" and
"UNLIM" are mutually exclusive. If
CONV-DEFAULT or a single
CONV-LIMIT is defined as UNLIM, the EntireX
Broker cannot determine the number of conversations to use in the calculation,
and the EntireX Broker cannot be started.
To calculate the number of servers automatically, ensure that the
SERVER-DEFAULT Broker attribute and the
SERVER-LIMIT service-specific attribute are not set to UNLIM
anywhere in the attribute file. Specify NUM-SERVER=AUTO and an appropriate
value for the SERVER-DEFAULT Broker attribute. The total number of server
buffers will be calculated using the value specified for each service.
For example:
DEFAULTS=BROKER NUM-SERVER=AUTO SERVER-DEFAULT=250 DEFAULTS=SERVICE CLASS=A, SERVER=A, SERVICE=A, SERVER-LIMIT=100 CLASS=B, SERVER=B, SERVICE=B CLASS=C, SERVER=C, SERVICE=C
To calculate the number of long message buffers automatically, ensure
that the LONG-BUFFER-DEFAULT Broker attribute and the
LONG-BUFFER-LIMIT service-specific attribute are not set to
UNLIM anywhere in the attribute file. Specify NUM-LONG-BUFFER=AUTO and an
appropriate value for the LONG-BUFFER-DEFAULT Broker attribute. The total
number of long message buffers will be calculated using the value specified for
each service.
For example:
DEFAULTS=BROKER NUM-LONG-BUFFER=AUTO LONG-BUFFER-DEFAULT=250 DEFAULTS=SERVICE CLASS=A, SERVER=A, SERVICE=A, LONG-BUFFER-LIMIT=100 CLASS=B, SERVER=B, SERVICE=B CLASS=C, SERVER=C, SERVICE=C
To calculate the number of short message buffers automatically, ensure
that the SHORT-BUFFER-DEFAULT Broker attribute and the
SHORT-BUFFER-LIMIT service-specific attribute are not set to
UNLIM anywhere in the attribute file. Specify NUM-SHORT-BUFFER=AUTO and an
appropriate value for the SHORT-BUFFER-DEFAULT Broker attribute. The total
number of short message buffers will be calculated using the value specified
for each service.
For example:
DEFAULTS=BROKER NUM-SHORT-BUFFER=AUTO SHORT-BUFFER-DEFAULT=250 DEFAULTS=SERVICE CLASS=A, SERVER=A, SERVICE=A CLASS=B, SERVER=B, SERVICE=B, SHORT-BUFFER-LIMIT=100 CLASS=C, SERVER=C, SERVICE=C
Dynamic memory management is a feature to handle changing Broker workload without any restart of the Broker task. It increases the availability of the Broker by using various memory pools for various Broker resources and by being able to use a variable number of pools for the resources.
If more memory is needed than currently available, another memory pool is allocated for the specific type of resource. If a particular memory pool is no longer used, it will be deallocated.
The following Broker attributes can be omitted if
DYNAMIC-MEMORY-MANAGEMENT=YES has been
defined:
NUM-CLIENT
NUM-CMDLOG-FILTER
NUM-COMBUF
NUM-CONV[ERSATION]
NUM-LONG[-BUFFER]
NUM-PUBLICATION
NUM-PUBLISHER
NUM-SERVER
NUM-SERVICE
NUM-SERVICE-EXTENSION
NUM-SHORT[-BUFFER]
NUM-SUBSCRIBER
NUM-SUBSCRIBER-TOTAL
NUM-TOPIC
NUM-TOPIC-EXTENSION
NUM-TOPIC-TOTAL
NUM-UOW|MAX-UOWS|MUOW
NUM-WQE
If you want statistics on allocation and deallocation operations in
Broker, you can configure Broker to create a storage report with the attribute
STORAGE-REPORT.
See Storage Report below.
Note:
To ensure a stabile environment, some pools of Broker are not deallocated automatically.
The first pools of type COMMUNICATION, CONVERSATION,
CONNECTION, HEAP, PARTICIPANT,
PARTICIPANT EXTENSION, SERVICE ATTRIBUTES,
SERVICE, SERVICE EXTENSION,
TIMEOUT QUEUE, TRANSLATION, WORK QUEUE are excluded from the automatic deallocation even when they have not been used for quite some time.
Large pools cannot be reallocated under some circumstances if the level of fragmentation in the address space has been increased
in the meantime.
Dynamic worker management is a feature to handle the fluctuating broker workload without restarting the Broker task.
It adjusts the number of running worker tasks according to current workload. The initial portion of worker tasks started
at Broker startup is still determined by NUM-WORKER.
If more workers are needed than currently available, another worker task is started. If a worker task is no longer needed, it will be stopped.
The following Broker attributes are used for the configuration if
DYNAMIC-WORKER-MANAGEMENT=YES
has been defined:
WORKER-MAX
WORKER-MIN
WORKER-NONACT
WORKER-QUEUE-DEPTH
WORKER-START-DELAY
The following two attributes are very performance-sensitive:
Attribute WORKER-QUEUE-DEPTH defines the number of unassigned user requests in the input queue before a new worker task is started.
Attribute WORKER-START-DELAY defines the time between the last worker task startup and the next check for another possible worker task startup. It is
needed to consider the time for activating a worker task.
Both attributes depend on the environment, in particular the underlying operating system and the hardware. The goal is to achieve high-performance user request processing without starting too many worker tasks.
A good starting point to achieve high performance is not to change the attributes and to observe the performance of the application programs after activating the dynamic worker management.
If broker attribute DYNAMIC-WORKER-MANAGEMENT=YES is set, operator commands are available under
z/OS
to deactivate and subsequently reactivate dynamic worker management.
The following section illustrates the two different modes of dynamic worker management:
DYNAMIC-WORKER-MANAGEMENT=YES NUM-WORKER = 5 WORKER-MIN = 1 WORKER-MAX = 32
Broker is started with 5 worker tasks and then dynamically varies the number of worker tasks within the range from WORKER-MIN=1 to WORKER-MAX=32 due to DYNAMIC-WORKER-MANAGEMENT=YES.
DYNAMIC-WORKER-MANAGEMENT=NO NUM-WORKER = 5 WORKER-MIN = 1 WORKER-MAX = 32
Broker is started with 5 worker tasks. The WORKER-MIN/MAX attributes are ignored due to DYNAMIC-WORKER-MANAGEMENT=NO.
You can create an optional report file that provides details about all activities to allocate or to deallocate memory pools. This section details how to create the report and provides a sample report.
See also Broker-specific attribute
STORAGE-REPORT.
Use Broker's global attribute
STORAGE-REPORT with the value
YES. If attribute value
YES is supplied, all memory pool operations will
be reported if the output mechanism is available. If the value
NO is specified, no report will be created.
DDNAME ETBSREP assigns the report file. Format
RECFM=FB, LRECL=121 is used.
Broker creates a file with the name
STORAGE.REPORT in the current working directory. If the
environment variable ETB_STORAGE_REPORT is
supplied, the file name specified in the environment variable will be used. If
Broker receives the command-line argument -r, the token following
argument -r will be used as the file name.
LINK-NAME ETBSREP assigns the report file. Format REC-FORM=V,
REC-SIZE=0, FILE-TYPE ISAM is used by default.
Logical unit SYS015 and logical file name ETBSREP
are used. Format RECORD-FORMAT=FB, RECORD-LENGTH=121 is used.
The following is an excerpt from a sample STORAGE report.
EntireX 8.1.0.00 STORAGE Report 2009-06-26 12:28:58 Page 1
Identifier Address Size Total Date Time Action
KERNEL POOL 0x25E48010 407184 bytes 407184 bytes 2009-06-26 12:28:58.768 Allocated
HEAP POOL 0x25EB4010 1050692 bytes 1457876 bytes 2009-06-26 12:28:58.769 Allocated
COMMUNICATION POOL 0x25FB5010 16781380 bytes 18239256 bytes 2009-06-26 12:28:58.769 Allocated
ACCOUNTING POOL 0x26FB7010 762052 bytes 19001308 bytes 2009-06-26 12:28:58.769 Allocated
BROKER POOL 0x27072010 61540 bytes 19062848 bytes 2009-06-26 12:28:58.775 Allocated
CONVERSATION POOL 0x27082010 368964 bytes 19431812 bytes 2009-06-26 12:28:58.775 Allocated
CONNECTION POOL 0x270DD010 233668 bytes 19665480 bytes 2009-06-26 12:28:58.779 Allocated
LONG MESSAGES POOL 0x27117010 4395204 bytes 24060684 bytes 2009-06-26 12:28:58.782 Allocated
SHORT MESSAGES POOL 0x27549010 3703876 bytes 27764560 bytes 2009-06-26 12:28:58.806 Allocated
PARTICIPANT POOL 0x278D2010 134244 bytes 27898804 bytes 2009-06-26 12:28:58.827 Allocated
PARTICIPANT EXTENSION POOL 0x278F3010 36996 bytes 27935800 bytes 2009-06-26 12:28:58.829 Allocated
PROXY QUEUE POOL 0x278FD010 26724 bytes 27962524 bytes 2009-06-26 12:28:58.829 Allocated
SERVICE ATTRIBUTES POOL 0x27904010 131668 bytes 28094192 bytes 2009-06-26 12:28:58.829 Allocated
SERVICE POOL 0x27925010 54372 bytes 28148564 bytes 2009-06-26 12:28:58.830 Allocated
SERVICE EXTENSION POOL 0x27933010 32900 bytes 28181464 bytes 2009-06-26 12:28:58.831 Allocated
TIMEOUT QUEUE POOL 0x2793C010 87268 bytes 28268732 bytes 2009-06-26 12:28:58.831 Allocated
TRANSLATION POOL 0x27952010 179300 bytes 28448032 bytes 2009-06-26 12:28:58.832 Allocated
UNIT OF WORK POOL 0x2797E010 176324 bytes 28624356 bytes 2009-06-26 12:28:58.834 Allocated
WORK QUEUE POOL 0x279AA010 391268 bytes 29015624 bytes 2009-06-26 12:28:58.835 Allocated
BLACKLIST POOL 0x27A0A010 42084 bytes 29057708 bytes 2009-06-26 12:28:58.838 Allocated
SUBSCRIPTION POOL 0x27A15010 344148 bytes 29401856 bytes 2009-06-26 12:28:58.839 Allocated
TOPIC ATTRIBUTES POOL 0x27A6A010 129620 bytes 29531476 bytes 2009-06-26 12:28:58.841 Allocated
TOPIC POOL 0x26FB6068 2952 bytes 29534428 bytes 2009-06-26 12:28:58.842 Allocated
TOPIC EXTENSION POOL 0x27A8A010 30852 bytes 29565280 bytes 2009-06-26 12:28:58.842 Allocated
PSTORE SUBSCRIBER POOL 0x27A92010 33892 bytes 29599172 bytes 2009-06-26 12:28:58.843 Allocated
PSTORE TOPIC POOL 0x27A9B010 19540 bytes 29618712 bytes 2009-06-26 12:28:58.843 Allocated
COMMUNICATION POOL 0x25FB5010 16781380 bytes 12837332 bytes 2009-06-26 12:30:58.514 Deallocated
ACCOUNTING POOL 0x26FB7010 762052 bytes 12075280 bytes 2009-06-26 12:30:58.515 Deallocated
BROKER POOL 0x27072010 61540 bytes 12013740 bytes 2009-06-26 12:30:58.516 Deallocated
CONVERSATION POOL 0x27082010 368964 bytes 11644776 bytes 2009-06-26 12:30:58.518 Deallocated
CONNECTION POOL 0x270DD010 233668 bytes 11411108 bytes 2009-06-26 12:30:58.519 Deallocated
LONG MESSAGES POOL 0x27117010 4395204 bytes 7015904 bytes 2009-06-26 12:30:58.520 Deallocated
SHORT MESSAGES POOL 0x27549010 3703876 bytes 3312028 bytes 2009-06-26 12:30:58.526 Deallocated
PROXY QUEUE POOL 0x278FD010 26724 bytes 3285304 bytes 2009-06-26 12:30:58.530 Deallocated
SUBSCRIPTION POOL 0x27A15010 344148 bytes 2941156 bytes 2009-06-26 12:30:58.530 Deallocated
TOPIC ATTRIBUTES POOL 0x27A6A010 129620 bytes 2811536 bytes 2009-06-26 12:30:58.531 Deallocated
TOPIC POOL 0x26FB6068 2952 bytes 2808584 bytes 2009-06-26 12:30:58.531 Deallocated
TOPIC EXTENSION POOL 0x27A8A010 30852 bytes 2777732 bytes 2009-06-26 12:30:58.531 Deallocated
TIMEOUT QUEUE POOL 0x2793C010 87268 bytes 2690464 bytes 2009-06-26 12:30:58.532 Deallocated
UNIT OF WORK POOL 0x2797E010 176324 bytes 2514140 bytes 2009-06-26 12:30:58.533 Deallocated
WORK QUEUE POOL 0x279AA010 391268 bytes 2122872 bytes 2009-06-26 12:30:58.533 Deallocated
BLACKLIST POOL 0x27A0A010 42084 bytes 2080788 bytes 2009-06-26 12:30:58.534 Deallocated
PSTORE SUBSCRIBER POOL 0x27A92010 33892 bytes 2046896 bytes 2009-06-26 12:30:58.534 Deallocated
PSTORE TOPIC POOL 0x27A9B010 19540 bytes 2027356 bytes 2009-06-26 12:30:58.534 Deallocated
PARTICIPANT POOL 0x278D2010 134244 bytes 1893112 bytes 2009-06-26 12:49:25.817 Deallocated
PARTICIPANT EXTENSION POOL 0x278F3010 36996 bytes 1856116 bytes 2009-06-26 12:49:25.818 Deallocated
SERVICE ATTRIBUTES POOL 0x27904010 131668 bytes 1724448 bytes 2009-06-26 12:49:25.818 Deallocated
SERVICE POOL 0x27925010 54372 bytes 1670076 bytes 2009-06-26 12:49:25.818 Deallocated
SERVICE EXTENSION POOL 0x27933010 32900 bytes 1637176 bytes 2009-06-26 12:49:25.819 Deallocated
TRANSLATION POOL 0x27952010 179300 bytes 1457876 bytes 2009-06-26 12:49:25.819 Deallocated
HEAP POOL 0x25EB4010 1050692 bytes 407184 bytes 2009-06-26 12:49:25.820 Deallocated
KERNEL POOL 0x25E48010 407184 bytes 0 bytes 2009-06-26 12:49:25.820 Deallocated
| Header | Description |
|---|---|
| Identifier | Name of the memory pool. |
| Address | Start address of the memory pool. |
| Size | Size of the memory pool. |
| Total | Total size of all obtained memory pools. |
| Date, Time | Date and time of the action. |
| Action | The action of Broker. The following actions are
currently supported: Allocated: memory pool is allocated . Deallocated: memory pool is deallocated. |
This table shows the maximum number of TCP/IP connections per communicator:
| Platform | Maximum Number of TCP/IP Connections per Communicator |
|---|---|
| AIX | 2,048 |
| BS2000/OSD | 2,048 |
| HP-UX | 2,048 |
| Linux | 4,096 |
| Solaris | 65,356 |
| Windows | 4,096 |
| z/OS | 16,384 |
| z/VSE | 2,048 |
With the Broker-specific attribute POLL these restrictions can be lifted under z/OS and UNIX.
See POLL.
See also MAX-CONNECTIONS under TCP-OBJECT (Struct INFO_TCP) under Information Reply Structures in the Broker CIS documentation.
Under z/OS, the following message may appear in the broker log:
ETBD0286 Diagnostic Values: accept: 124, EDC5124I Too many open files.errno2: 84607302 050B0146
The most common reason for this TCP/IP Communicator diagnostic message is the limitation of open files per user.
The value of MAXFILEPROC in the BPXPRM00 parmlib
member should be greater than the expected number of TCP/IP connections.
Under UNIX, you can use the following command to display the maximum number of open files in the operating system shell.
ulimit -n
This value should be greater than the expected number of TCP/IP connections.