Displays system-wide resolver cache information. This information is not specific to the TCP/IP stack whose name was specified on the TCp/-p target parameter or to the default TCP/IP stack. Statistical information, such as number of record entries or number of cache queries, can be retrieved, or detailed information about some or all of the cache entries can be retrieved. Resolver caching is configured using resolver configuration statements in the resolver setup file. For more information about resolver caching, see details about resolver caching in z/OS Communications Server: IP Configuration Guide.
.-SUMmary--------------. >>-+----------------------+------------------------------------>< +-DETAIL--+----------+-+ | '-NEGative-' | '-SUMmary--+-----+-----' '-DNS-'
Provide the report for a specific TCP/IP address space by using the TCp tcpname option. See The Netstat command target for more information about the TCp parameter.
The default output option displays the output on the user terminal. For other options, see Netstat command output.
.-SUMmary--------------. >>-+----------------------+------------------------------------>< +-DETAIL--+----------+-+ | '-NEGative-' | '-SUMmary--+-----+-----' '-DNS-'
Provide the report for a specific TCP/IP address space by using the TCp tcpname option. See The Netstat command target for more information about the -p parameter.
The default output option displays the output on the user terminal. For other options, see Netstat command output.
Restriction: The filter value does not support wildcard characters.
Restriction: The HOSTName/-H filter applies only to the IPAddress to HostName translation portion of the report
The filter value for HOSTName/-H can be a complete string or a partial string that can use wildcard characters. A wildcard character can be an asterisk (*), which matches a null string or any character or character string, in the same position. A wildcard character can also be a question mark (?), which matches any single character in the same position. For example, the string searchee matches with the search value *ar?he*, but the string searhee does not match with the search value *ar?he*.
Tip: The filter value host21 is equal to host21.* but host21 is not equal to host21* because host21* also matches cache entries such as host211.ibm.com and host2134.ibm.com.
When you use the z/OS UNIX netstat/onetstat command in a z/OS UNIX shell environment, using a z/OS UNIX MVS™ special character in a character string might cause an unpredictable result. If you want to use a z/OS UNIX MVS special character in a character string, surround the character string with single quotation marks (') quotation marks ("). For example, to use an asterisk (*) in the host name, cat.* for the -H filter, issue the command as: netstat -q -H 'cat.*' or netstat -q -H "cat.*".
Use the RESCache/-q filters only when you use the DETAIL modifier. Specifying a filter with the SUMMARY modifier does not affect the report output.
NETSTAT RESCACHE SUMMARY
Display general system statistics for resolver cache operations
NETSTAT RESCACHE SUMMARY DNS
Display general system statistics for resolver cache operations, plus individual
statistics for each DNS name server that has provided information currently
stored in the cache.
NETSTAT RESCACHE DETAIL
Display detailed information for all unexpired entries that are currently
in the resolver cache.
NETSTAT RESCACHE DETAIL (DNSADDR 10.7.7.7
Display detailed information for all unexpired entries that are currently
in the resolver cache that were provided by the DNS name server at IP address 10.7.7.7
NETSTAT RESCACHE DETAIL (HOSTName hostname.domain
Display detailed information for all HostName to IPAddress resolution cache
entries currently in the resolver cache that were acquired using host name
hostname.domain as the target resource for the resolver query.
NETSTAT RESCACHE DETAIL (HOSTName hostname.*
Display detailed information for all HostName to IPAddress resolution cache
entries currently in the resolver cache that were acquired using a host name matching
the hostname.* pattern string as the target resource for the resolver query.
NETSTAT RESCACHE DETAIL (IPAddr 10.9.9.9
Display detailed information for all IPAddress to HostName resolution
cache entries currently in the resolver cache that were acquired using IP address
10.9.9.9 as the target resource for the resolver query.
NETSTAT RESCACHE DETAIL NEGATIVE
Display detailed information for all negative cache entries in the resolver cache
netstat -q SUMMARY
netstat -q SUMMARY DNS
netstat -q DETAIL
netstat -q DETAIL -Q 10.7.7.7
netstat -q DETAIL -H hostname.domain
netstat -q DETAIL -H 'hostname.*'
netstat -q DETAIL -I 10.9.9.9
netstat -q DETAIL NEGATIVE
The following examples are generated by using the TSO NETSTAT command. Using the z/OS UNIX netstat command displays the data in the same format as the TSO NETSTAT command.
NETSTAT RESCACHE or NETSTAT RESCACHE SUMMARY
MVS TCP/IP NETSTAT CS V2R1 TCPIP Name: TCPCS 15:12:31
Storage Usage:
Maximum: 10M
Current: 203K MaxUsed: 1M
Cache Usage:
Total Number of entries: 64
Non-NX entries: 44
A: 20 AAAA: 13 PTR: 11
NX entries: 20
A: 9 AAAA: 2 PTR: 9
Queries: 112 Hits: 34
SuccessRatio: 30%
NETSTAT RESCACHE SUMMARY DNS MVS TCP/IP NETSTAT CS V2R1 TCPIP Name: TCPCS 15:12:45
Storage Usage:
Maximum: 10M
Current: 203K MaxUsed: 1M
Cache Usage:
Total Number of entries: 64
Non-NX entries: 44
A: 20 AAAA: 13 PTR: 11
NX entries: 20
A: 9 AAAA: 2 PTR: 9
Queries: 112 Hits: 34
SuccessRatio: 30%
DNS address: 19.47.135.295
Total Number of entries: 54
Non-NX entries: 39
A: 18 AAAA: 11 PTR: 10
NX entries: 15
A: 7 AAAA: 2 PTR: 6
References: 77 Hits: 21
DNS address: 19.52.206.22
Total Number of entries: 10
Non-NX entries: 5
A: 2 AAAA: 2 PTR: 1
NX entries: 5
A: 2 AAAA: 0 PTR: 3
References: 43 Hits: 13
NETSTAT RESCACHE
DETAIL MVS TCP/IP NETSTAT CS V2R1 TCPIP Name: TCPCS 15:12:51
HostName to IPAddress translation
---------------------------------
HostName: HOSTNAME1
DNS IPAddress: 19.47.135.295
DNS Record Type: T_A
Canonical Name: ***NA***
Cache Time: 10/27/2011 18:44:43
Expired Time: 10/27/2011 19:44:33
Hits: 0
IPAddress: ***NA***
HostName: HOSTNAME4.TCP.RALEIGH.IBM.COM
DNS IPAddress: 19.47.135.295
DNS Record Type: T_A
Canonical Name: hostname4.tcp.raleigh.ibm.com
Cache Time: 10/27/2011 18:36:51
Expired Time: 10/28/2011 14:25:16
Hits: 0
IPAddress: 29.72.105.195
29.72.105.196
29.72.105.197
HostName: HOSTNAME1.TCP.RALEIGH.IBM.COM
DNS IPAddress: 19.47.135.295
DNS Record Type: T_A
Canonical Name: ***NA***
Cache Time: 10/27/2011 18:44:38
Expired Time: 10/27/2011 19:44:28
Hits: 0
IPAddress: ***NA***
HostName: HOSTNAME5.TCP.RALEIGH.IBM.COM
DNS IPAddress: 19.47.135.295
DNS Record Type: T_A
Canonical Name: hostname5.pok.ibm.com
Cache Time: 10/27/2011 18:43:22
Expired Time: 10/27/2011 20:09:38
Hits: 0
IPAddress: 29.236.231.69
HostName: WWW.NEWSPAPER.COM
DNS IPAddress: 19.52.206.22
DNS Record Type: T_A
Canonical Name: newspaper.com
Cache Time: 10/27/2011 19:05:29
Expired Time: 10/27/2011 20:05:29
Hits: 0
IPAddress: 125.152.8.134
HostName: HOSTNAME5.TCP.RALEIGH.IBM.COM
DNS IPAddress: 19.52.206.22
DNS Record Type: T_A
Canonical Name: hostname55.pok.ibm.com
Cache Time: 10/27/2011 19:06:36
Expired Time: 10/27/2011 20:09:37
Hits: 1
IPAddress: 29.236.231.69
HostName: WWW.STATE1.GOV
DNS IPAddress: 19.52.206.22
DNS Record Type: T_AAAA
Canonical Name: state1.gov
Cache Time: 10/27/2011 19:09:24
Expired Time: 10/27/2011 19:19:24
Hits: 0
IPAddress: 144::227:12:34:76
HostName: WWW.COLLEGE1.EDU
DNS IPAddress: 19.52.206.22
DNS Record Type: T_AAAA
Canonical Name: www.college1.edu
Cache Time: 10/27/2011 19:08:45
Expired Time: 10/27/2011 19:18:45
Hits: 0
IPAddress: 1004::251:133:180:120
1004::251:133:180:121
HostName: WWW.COMPANY.COM
DNS IPAddress: 19.52.206.22
DNS Record Type: T_AAAA
Canonical Name: ***NA***
Cache Time: 10/27/2011 19:11:20
Expired Time: 10/27/2011 19:28:00
Hits: 2
IPAddress: ***NA***
IPAddress to HostName translation
---------------------------------
IPAddress: 930::159:84:218:223
DNS IPAddress: 19.47.135.295
DNS Record Type: T_PTR
Cache Time: 10/27/2011 19:07:43
Expired Time: 10/27/2011 19:17:43
Hits: 1
HostName: hostipv6-223.218.84.150.company.com
IPAddress: 152.12.39.164
DNS IPAddress: 19.52.206.22
DNS Record Type: T_PTR
Cache Time: 10/27/2011 19:05:59
Expired Time: 10/27/2011 20:05:59
Hits: 1
HostName: ***NA***
IPAddress: 159.84.218.223
DNS IPAddress: 19.52.206.22
DNS Record Type: T_PTR
Cache Time: 10/27/2011 19:05:43
Expired Time: 10/27/2011 19:15:43
Hits: 1
HostName: hostvalue-223.218.84.159.company.com
IPAddress: 152.152.31.134
DNS IPAddress: 19.52.206.22
DNS Record Type: T_PTR
Cache Time: 10/27/2011 19:05:59
Expired Time: 10/27/2011 20:05:59
Hits: 1
HostName: namemh.media.com
Guideline: A single resolver API call, for example, Getaddrinfo, might result in multiple queries to the resolver cache. Separate cache queries are attempted for IPv4 and IPv6 information. Separate cache queries are also attempted for different domains if the SEARCH resolver configuration statement specifies that different domains should be appended to the input host name value for search purposes.
Guideline: A single cache query attempt might result in multiple queries of different collections of information provided by the name server. You can use the NSINTERADDR resolver configuration statement to specify which name servers should be queried to obtain information about the target resource, and in which order they should be queried. The resolver cache uses the same NSINTERADDR list to determine which collections of information provided by the name server to examine for a specific cache query. If no response information is found in the collection of information that is provided by the first name server in the NSINTERADDR list, the collection of information that is provided by the second name server in the list is checked, and so on.
If the first name server in the NSINTERADDR list is the primary name server for the installation, the number of references for that name server should be much higher than the number of references for the other name servers in the list. Most of the resolver queries should, during normal operation, be directed to the primary name server, and therefore most information in the resolver cache should be provided by the primary name server. A comparatively small number of references for the primary name server, compared to the secondary name servers, suggests that the primary name server might not be active all the time, or that most of the cache queries are not successful, because the resolver cache is examining more than just the primary name server's collection of responses as part of a single cache query.
Guideline: The resolver cache logic does not automatically delete cache entries when the TTL time expires. The cache entries are deleted when a subsequent query for the host name is received or they are deleted as part of periodic storage cleanup processing.
Guideline: The resolver cache logic does not automatically delete cache entries when the TTL time expires. The cache entries are deleted when a subsequent query for the IP address is received, or they are deleted as part of periodic storage cleanup processing.
If this entry represents negative cache information, then the value *** NA *** is displayed instead of an IP address.