I'm running Web Agent ca-wa-12.52-sp01-cr05-linux-x86-64.bin on a Red
Hat 6. But when I start it, Oracle HTTP Server fails to start.  In the
log file, I can read in the following :

/home/ohs/Oracle/Middleware/Oracle_Home/user_projects/domains/base_domain/system_components/OHS/ohs_nm.log

<2017-08-30 15:19:32> <INFO> <OHS-4018> <Starting server ohs1>
<2017-08-30 15:19:32> <INFO> <OHS-0> <Running /home/ohs/Oracle/Middleware/Oracle_Home/ohs/bin/httpd.sh httpd.worker -k start -f /home/ohs/Oracle/Middleware/Oracle_Home/user_projects/domains/base_domain/config/fmwconfig/components/OHS/instances/ohs1/httpd.conf>
<2017-08-30 15:19:32> <INFO> <OHS-0> <httpd: Syntax error on line 67 of /home/ohs/Oracle/Middleware/Oracle_Home/user_projects/domains/base_domain/config/fmwconfig/components/OHS/instances/ohs1/httpd.conf: Cannot load /opt/CA/webagent/bin/libmod_sm22.so into server: libsmerrlog
.so: cannot open shared object file: No such file or directory>
<2017-08-30 15:19:32> <SEVERE> <OHS-0> <Failed to start the server ohs1>

How can I solve this ?

You need to run the Web Agent configurator to integrate the Oracle
HTTP Server with the Web Agent. The configurator on Linux has file
name as : ca-wa-config.bin

To configure properly the Web Agent on Oracle HTTP Server 12c, with
the Web Agent configurator, you need to find where the OHS server is
installed and you need to know the exact version of the Apache that
the OHS Server runs :

In this sample, the Web Server is installed in

/home/ohs/Oracle/Middleware/Oracle_Home/user_projects/domains/base_domain/config/fmwconfig/components/OHS/instances/ohs1

and the Oracle HTTP Server (Apache) is 2.2.22 64bit.

As ohs user (or the one you gave for the installation of OHS) those
command to know the exact Apache version :

  $ export LD_LIBRARY_PATH=/home/ohs/Oracle/Middleware/Oracle_Home/lib:/home/ohs/Oracle/Middleware/Oracle_Home/ohs/lib:${LD_LIBRARY_PATH}
  $ /home/ohs/Oracle/Middleware/Oracle_Home/ohs/bin/httpd.worker -V
  Server version: Oracle-HTTP-Server/2.2.22 (Unix)
  Server built:   Jun 11 2013 13:18:04
  Server Label:   APACHE_12.1.2.0.0_LINUX.X64_130611.0942
  Server's Module Magic Number: 20051115:30
  Server loaded:  APR 1.4.5, APR-Util 1.4.1
  Compiled using: APR 1.4.5, APR-Util 1.4.1
  Architecture:   64-bit
  Server MPM:     Worker
    threaded:     yes (fixed thread count)
      forked:     yes (variable process count)
  Server compiled with....
   -D APACHE_MPM_DIR="server/mpm/worker"
   -D APR_HAS_SENDFILE
   -D APR_HAS_MMAP
   -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
   -D APR_USE_SYSVSEM_SERIALIZE
   -D APR_USE_PTHREAD_SERIALIZE
   -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
   -D APR_HAS_OTHER_CHILD
   -D AP_HAVE_RELIABLE_PIPED_LOGS
   -D DYNAMIC_MODULE_LIMIT=128
   -D HTTPD_ROOT="$(APACHE2_HOME)"
   -D SUEXEC_BIN="$(APACHE2_HOME)/bin/suexec"
   -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
   -D DEFAULT_ERRORLOG="logs/error_log"
   -D AP_TYPES_CONFIG_FILE="conf/mime.types"
   -D SERVER_CONFIG_FILE="conf/httpd.conf"

Then you run the Web Agent configurator that way to have the Oracle
HTTP Server fully configured with the Web Agent (this come from
configuration of Web Agent 12.52SP1CR05 64bit on RedHat 6)

In this sample, we assume the host has been registered already with
the Policy Server and the SmHost.conf is already created.

as root :

  # cd /opt/CA/webagent/install_config_info
  # source ../ca_wa_env.sh
  # ./ca-wa-config.bin -i console

  Preparing to install...
  Extracting the JRE from the installer archive...
  Unpacking the JRE...
  Extracting the installation resources from the installer archive...
  Configuring the installer for this system's environment...

  Launching installer...

  ===============================================================================
  CA SiteMinder Web Agent Configuration            (created with InstallAnywhere)
  -------------------------------------------------------------------------------

  Preparing CONSOLE Mode Installation...




  ===============================================================================
  Host Registration
  -----------------

  Select '1' to register this Agent with the Policy Server.

  Select '2' to register later.



  Note:  You cannot select choice 1 and 2 at the same time.



  Warning:  You have already registered this Agent with a Policy Server.

    ->1- Yes, I would like to do Host Registration now.
      2- No, I would like to do Host Registration later.

  ENTER A COMMA-SEPARATED LIST OF NUMBERS REPRESENTING THE DESIRED CHOICES, OR
     PRESS <ENTER> TO ACCEPT THE DEFAULT: 2



  ===============================================================================
  Select Web Server(s)
  --------------------

  Select which Web Server(s) you want to configure as a Web Agent.

  You will have to enter a path for each selected web server.

  Note:   If you have an Apache-based Web server, please select the Apache Web
  Server option.

      1- Apache Web Server
      2- Domino Web Server
    ->3- iPlanet or Sun ONE Web Server

  ENTER A COMMA-SEPARATED LIST OF NUMBERS REPRESENTING THE DESIRED CHOICES, OR
     PRESS <ENTER> TO ACCEPT THE DEFAULT: 1



  ===============================================================================
  Apache Web Server path
  ----------------------

  Enter the root path of where Apache Web server installed.

  Please enter path (Default: ): /home/ohs/Oracle/Middleware/Oracle_Home/user_projects/domains/base_domain/config/fmwconfig/components/OHS/instances/ohs1



  ===============================================================================
  Apache Web Server Failure
  -------------------------

  Apache webserver does not exist at: /home/ohs/Oracle/Middleware/Oracle_Home/us
  er_projects/domains/base_domain/config/fmwconfig/components/OHS/instances/ohs1.



  Note:  If you have any other Apache Web servers that may not be detected by
  the Wizard, please select choice "2".

    ->1- I would like to re-enter the Apache Server Root.
      2- I would like to enter a specific configuration path.
      3- I don't have an Apache Web server.

  ENTER THE NUMBER OF THE DESIRED CHOICE, OR PRESS <ENTER> TO ACCEPT THE
     DEFAULT: 2


  ===============================================================================
  Apache Web Server path
  ----------------------

  Please enter the configuration path for Apache Web server.

  Please enter path (Default: ): /home/ohs/Oracle/Middleware/Oracle_Home/user_projects/domains/base_domain/config/fmwconfig/components/OHS/instances/ohs1



  ===============================================================================
  Apache Version
  --------------

  Please select a choice for the Apache version.

      1- Apache version 1.x
      2- Apache version 2.x
      3- Apache version 2.2.x
      4- Apache version 2.4.x

  ENTER THE NUMBER OF THE DESIRED CHOICE: 3



  ===============================================================================
  Apache Server Type
  ------------------

  Please select one of the following appropriately match your previous selection

      1- Oracle HTTP Server
      2- IBM HTTP Server
      3- HP Apache
      4- ASF/RedHat Apache
      5- RedHat JWS HTTP Server

  ENTER THE NUMBER OF THE DESIRED CHOICE: 1



  ===============================================================================
  Select Web Server(s)
  --------------------

      1- [x] Oracle 12.0

  Select the web server(s) you wish to preserve or configure/reconfigure as
     Web Agent(s). Enter a comma-separated list of numbers representing the
     desired choices. Already configured web servers are marked as [x] in the
     above list, you can un-configure or skip these web servers in next steps by
     not listing them in comma-separated list here.: 1


  ===============================================================================
  Select One or More Instances to Overwrite
  -----------------------------------------

      1- Oracle 12.0
      2- PRESERVE ALL

  The following web server instance(s) have been previously configured as Web
     Agent(s).  Select which web server instance(s) you wish to overwrite. 
     Select the last option to preserve them all.  Enter a comma-separated list
     of numbers representing the desired choices.: 1


  ===============================================================================
  Select One or More Instances to Unconfigure
  -------------------------------------------




  ===============================================================================
  Agent Configuration Object
  --------------------------

  Enter the name of an Agent Configuration Object that defines the configuration
  parameters which the Web Agent will use for Oracle 12.0.

  Agent Configuration Object (Default: AgentObj): ohs



  ===============================================================================
  SSL Authentication
  ------------------

  The following SSL configurations are available for this web server.  If the
  Web Agent will be providing advanced authentication, select which
  configuration it will use to configure Oracle 12.0.

    ->1- HTTP Basic over SSL
      2- X509 Client Certificate
      3- X509 Client Certificate and HTTP Basic
      4- X509 Client Certificate or HTTP Basic
      5- X509 Client Certificate or Form
      6- X509 Client Certificate and Form
      7- No advanced authentication

  ENTER THE NUMBER FOR YOUR CHOICE, OR PRESS <ENTER> TO ACCEPT THE DEFAULT:: 7



  ===============================================================================
  Webagent Enable option
  ----------------------

  Please select Yes to Enable the WebAgent

      1- Yes
    ->2- No

  ENTER THE NUMBER FOR YOUR CHOICE, OR PRESS <ENTER> TO ACCEPT THE DEFAULT:: 1



  ===============================================================================
  Web Server Configuration Summary
  --------------------------------

  Please confirm the configuration selection.  Accept the configuration and
  press 'Enter' to continue.  To change one or more settings, select 'Previous'.
  Select 'Cancel' will exit the configuration.



  Configure the following webserver(s):
  Apache Server:
  Oracle 12.0
  Agent Configuration Object: ohs
  SSL Authentication type: No advanced authentication



  IS WebAgent Enabled:  YES




  Please enter a choice.

    ->1- Continue
      2- Previous
      3- Cancel

  ENTER THE NUMBER OF THE DESIRED CHOICE, OR PRESS <ENTER> TO ACCEPT THE
     DEFAULT: 1


  ===============================================================================
  Installing...
  -------------

   [==================|==================|==================|==================]
   [------------------|------------------|------------------|------------------]



  ===============================================================================
  Configuration Complete
  ----------------------

  Congratulations! CA SiteMinder Web Agent Configuration has been successfully
  configured.

  PRESS <ENTER> TO EXIT THE INSTALLER:

# chown -R ohs.ohs /home/ohs
# chown -R ohs.ohs /opt/CA/webagent

Then to start and stop the server as ohs user :

  $ cd /home/ohs/Oracle/Middleware/Oracle_Home/user_projects/domains/base_domain/bin
  $ nohup ./startNodeManager.sh > nm.out &
  $ ./startComponent.sh ohs1
  $ ./stopComponent.sh ohs1

And you can access the default page of the Oracle HTTP Server from your Windows PC :

c:\> start /B iexplore http://<Server Name>.example.com:7777/

     Oracle HTTP Server 12c is based on the proven, open source Apache HTTP
     Server technology and provides the framework for hosting static,
     dynamic web pages and for front-ending Oracle Fusion Middleware
     Applications.

You can check the entire configuration after by reading this technotes :

How to configure Single Sign-On Webagent for OHS 12c manually

https://ca-broadcom.wolkenservicedesk.com/external/article?articleId=44111