Symptoms:
1) SAP job status updates and new job submissions stopped or jobs go to an Unknown state
2) The Control-M/Agent goes Unavailable
3) The Control-M for SAP Connection Profile goes Unavailable

4) Unable to access to Connection Profiles if it's a new Control-M for SAP installation

Example log or Job messages:

"Failed to connect to Control-M/CM for SAP. Maximum connection retries reached (RecoveryMaxRetry)."

AT log from ctm/proclog
1003 08:42:27:423 AT:OS_FILE_fopen started : ./cm/SAP/exe/../data/CTMSAP_container_conf.xml. mode=4
1003 08:42:27:423 AT:OS_FILE_fopen failed to open file: ./cm/SAP/exe/../data/CTMSAP_container_conf.xml. mode: r. errno=24, Too many open files
1003 08:42:28:424 AT:ErrorSet: Maximum connection retries reached (RecoveryMaxRetry).
1003 08:42:28:424 AT:ErrorSet: Failed to connect to Control-M/CM for SAP. Maximum connection retries reached (RecoveryMaxRetry).
1003 08:42:28:424 AT:Failed in remoting.call()

AS log from ctm/proclog
1001 00:34:32:174 AS:getAccountStatus: Failed to connect to account 'Account Name'
1001 00:34:32:174 AS:ErrorSet: Failed to connect to account 'Account Name'
1001 00:34:32:174 AS:getAccountStatus: Account Account_Name is UNAVAILABLE
1001 00:34:32:174 AS:BE_COMMON_replace_white_chars: In string :'Failed to connect to account 'Account Name'', to replace with char: '.'

Review each of the items below for possible solutions, depending on the symptoms you see.

1) Check the ulimit value for descriptors (aka "open files") for the user running the Control-M/Agent.
For example, if the Agent runs as root, check "open files" for the root user.
If the Agent runs as "ctmagent", check this user for "open files

Run the ulimit or limit command depending on the shell used.
If using c-shell:   limit descriptors
If using bash, ksh, ulimit -n

descriptors  1024
open files (-n) 1024

The Control-M Installation Guide recommends a minimum value of 4096. 
Increasing the value to 4096 or above will avoid the issue happening in future.  Please note on very busy Agent machine the value might need to be higher than the minimum recommendation


2) Verify the value of RecoveryMaxRetry in the ctm/cm/SAP/data/CTMSAP_container_conf.xml file.
The default is 30 but if this value has been lowered that may be causing the message.
Restore the value back to 30 if it was changed and stop the Control-M/Agent and verify that the Control-M for SAP java container is down with the command:  sapcmbe.sh status

3) Verify the JCO port is not problematic in the Operating System
  a) sapcmbe.sh status
  b) note the port mentioned above and run the command:   netstat -an | grep ####
  c) if may TIME_WAIT or SYN_PORT activities are listed, it may be necessary to reboot the system to clear any port issues

4) Make sure the latest Fix Pack or Patch is installed for Control-M for SAP
If possible, install or upgrade to the latest available Control-M for SAP version.

5) Set the Load Balancing Algorithm to "SAP Default"
a) In the CCM right click on the Control-M for SAP entry and select Configuration Management
b) Set the Load Balancing Algorithm to "SAP Default"
3) Restart the JCO with the command:  sapcmbe.sh stop    (no need to restart as it starts automatically)

6) If it's a new Control-M for SAP installation make sure the JCo libraries were placed on the Control-M/Agent machine

This procedure is explained in section "Downloading the sapjco3.jar and sapjco3 C Library Files" from the documentation:

https://documents.bmc.com/supportu/9.0.21.300/en-US/Documentation/SAP_Post-installation.htm#Downloadingthesapjco3jarandsapjco3CLibraryFiles