{
    "mode": "man",
    "parameter": "SCACHE",
    "section": "8postfix",
    "url": "https://www.chedong.com/phpMan.php/man/SCACHE/8postfix/json",
    "generated": "2026-06-14T12:36:18Z",
    "synopsis": "scache [generic Postfix daemon options]",
    "sections": {
        "NAME": {
            "content": "scache - Postfix shared connection cache server\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "scache [generic Postfix daemon options]\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "The  scache(8) server maintains a shared multi-connection cache. This information can be used\nby, for example, Postfix SMTP clients or other Postfix delivery agents.\n\nThe connection cache is organized into logical destination names,  physical  endpoint  names,\nand connections.\n\nAs a specific example, logical SMTP destinations specify (transport, domain, port), and phys‐\nical SMTP endpoints specify (transport, IP address, port).  An SMTP connection may  be  saved\nafter a successful mail transaction.\n\nIn  the  general  case, one logical destination may refer to zero or more physical endpoints,\none physical endpoint may be referenced by zero or more logical destinations,  and  one  end‐\npoint may refer to zero or more connections.\n\nThe  exact  syntax  of  a  logical destination or endpoint name is application dependent; the\nscache(8) server does not care.  A connection is stored as a file  descriptor  together  with\napplication-dependent  information  that is needed to re-activate a connection object. Again,\nthe scache(8) server is completely unaware of the details of that information.\n\nAll information is stored with a finite time to live (ttl).  The connection cache daemon ter‐\nminates when no client is connected for maxidle time units.\n\nThis server implements the following requests:\n\nsaveendp ttl endpoint endpointproperties filedescriptor\nSave  the  specified  file descriptor and connection property data under the specified\nendpoint name. The endpoint properties are used by the client to re-activate a  passi‐\nvated connection object.\n\nfindendp endpoint\nLook up cached properties and a cached file descriptor for the specified endpoint.\n\nsavedest ttl destination destinationproperties endpoint\nSave  the  binding between a logical destination and an endpoint under the destination\nname, together with destination specific connection properties. The destination  prop‐\nerties are used by the client to re-activate a passivated connection object.\n\nfinddest destination\nLook  up  cached destination properties, cached endpoint properties, and a cached file\ndescriptor for the specified logical destination.\n",
            "subsections": []
        },
        "SECURITY": {
            "content": "The scache(8) server is not security-sensitive. It does not talk to the network, and it  does\nnot talk to local users.  The scache(8) server can run chrooted at fixed low privilege.\n\nThe  scache(8) server is not a trusted process. It must not be used to store information that\nis security sensitive.\n",
            "subsections": []
        },
        "DIAGNOSTICS": {
            "content": "Problems and transactions are logged to syslogd(8) or postlogd(8).\n",
            "subsections": []
        },
        "BUGS": {
            "content": "The session cache cannot be shared among multiple machines.\n\nWhen a connection expires from the cache, it is closed without the appropriate protocol  spe‐\ncific handshake.\n",
            "subsections": []
        },
        "CONFIGURATION PARAMETERS": {
            "content": "Changes  to main.cf are picked up automatically as scache(8) processes run for only a limited\namount of time. Use the command \"postfix reload\" to speed up a change.\n\nThe text below provides only a parameter summary. See postconf(5) for more details  including\nexamples.\n",
            "subsections": []
        },
        "RESOURCE CONTROLS": {
            "content": "connectioncachettllimit (2s)\nThe maximal time-to-live value that the scache(8) connection cache server allows.\n\nconnectioncachestatusupdatetime (600s)\nHow  frequently  the  scache(8) server logs usage statistics with connection cache hit\nand miss rates for logical destinations and for physical endpoints.\n",
            "subsections": []
        },
        "MISCELLANEOUS CONTROLS": {
            "content": "configdirectory (see 'postconf -d' output)\nThe default location of the Postfix main.cf and master.cf configuration files.\n\ndaemontimeout (18000s)\nHow much time a Postfix daemon process may take to handle a request before it is  ter‐\nminated by a built-in watchdog timer.\n\nipctimeout (3600s)\nThe  time  limit  for  sending or receiving information over an internal communication\nchannel.\n\nmaxidle (100s)\nThe maximum amount of time that an idle Postfix daemon process waits for  an  incoming\nconnection before terminating voluntarily.\n\nprocessid (read-only)\nThe process ID of a Postfix command or daemon process.\n\nprocessname (read-only)\nThe process name of a Postfix command or daemon process.\n\nsyslogfacility (mail)\nThe syslog facility of Postfix logging.\n\nsyslogname (see 'postconf -d' output)\nA  prefix  that is prepended to the process name in syslog records, so that, for exam‐\nple, \"smtpd\" becomes \"prefix/smtpd\".\n\nAvailable in Postfix 3.3 and later:\n\nservicename (read-only)\nThe master.cf service name of a Postfix daemon process.\n",
            "subsections": []
        },
        "SEE ALSO": {
            "content": "smtp(8), SMTP client\npostconf(5), configuration parameters\nmaster(8), process manager\npostlogd(8), Postfix logging\nsyslogd(8), system logging\n",
            "subsections": []
        },
        "README FILES": {
            "content": "Use \"postconf readmedirectory\" or \"postconf htmldirectory\" to locate this information.\nCONNECTIONCACHEREADME, Postfix connection cache\n",
            "subsections": []
        },
        "LICENSE": {
            "content": "The Secure Mailer license must be distributed with this software.\n",
            "subsections": []
        },
        "HISTORY": {
            "content": "This service was introduced with Postfix version 2.2.\n\nAUTHOR(S)\nWietse Venema\nIBM T.J. Watson Research\nP.O. Box 704\nYorktown Heights, NY 10598, USA\n\nWietse Venema\nGoogle, Inc.\n111 8th Avenue\nNew York, NY 10011, USA\n\n\n\nSCACHE(8postfix)",
            "subsections": []
        }
    },
    "summary": "scache - Postfix shared connection cache server",
    "flags": [],
    "examples": [],
    "see_also": [
        {
            "name": "smtp",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/smtp/8/json"
        },
        {
            "name": "postconf",
            "section": "5",
            "url": "https://www.chedong.com/phpMan.php/man/postconf/5/json"
        },
        {
            "name": "master",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/master/8/json"
        },
        {
            "name": "postlogd",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/postlogd/8/json"
        },
        {
            "name": "syslogd",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/syslogd/8/json"
        }
    ]
}