Why "setkey -D" command displays “recv: Resource temporarily unavailable” error string after displaying all established SAs.

Issue

• We are working on IPSec SA establishment, In our implementation we are managing the Security Association Database (SAD) and Security Policy Database (SPD) entries of the kernel via scripts triggered through our application.
• We successfully created SAs and SPs entries but we are facing issues that after establishment of approximately 520 SAs, new SAs were not created.
• setkey –D command displays “recv: Resource temporarily unavailable” error string after displaying all established SAs.
• Why large number of SAs are not created in IpSec in RHEL 5?